Update phpunit/phpunit requirement from 4.* to 8.*

[dependabot-preview]

Updates the requirements on phpunit/phpunit to permit the latest version.

Changelog

Sourced from phpunit/phpunit's changelog.

[8.3.5] - 2019-09-14

Fixed

• Fixed #3745: Performance degradation with test doubles
• Fixed #3801: Class constant as default parameter is undefined
• Fixed #3807: Fixed message of exception raised by MockBuilder::addMethods()
• Fixed #3834: Trailing slash breaks code coverage on Windows

[8.3.4] - 2019-08-11

Changed

• Implemented #3788: Cast exception message to string

Fixed

• Fixed #3772: Process Isolation does not work when PHPDBG is used

[8.3.3] - 2019-08-03

Fixed

• Fixed #3781: MockBuilder::addMethods() and MockBuilder::onlyMethods() do not handle empty parameter array correctly

[8.3.2] - 2019-08-02

Fixed

• More work on the fix for #3774: Restored name of PHPUnit\Framework\Error\Deprecated

[8.3.1] - 2019-08-02

Fixed

• Fixed #3774: PHP errors, notices, etc. cannot be tested anymore with PHPUnit 8.3

[8.3.0] - 2019-08-02

Added

• Implemented #3687: Introduce MockBuilder::addMethods() and MockBuilder::onlyMethods() as alternatives to MockBuilder::setMethods()
• Implemented #3741: Format class names as well as method names in TestDox output
• Implemented #3748: Add option to sort tests based on information from @small, @medium, and @large
• Added TestCase::getActualOutputForAssertion() as a wrapper for TestCase::getActualOutput() to prevent a test being marked as risky when it prints output and that output is not expected using TestCase::expectOutputString() or TestCase::expectOutputRegEx()

Changed

• Implemented #2015: Prefix all code bundled in PHAR distribution with random/unique namespace
• Implemented #3503: The error handler has been refactored to not rely on global state

... (truncated)

Commits

• 302faed Prepare release
• fcf2eb6 Merge branch '7.5' into 8.3
• 316afa6 Prepare release
• 5c959e3 Update Psalm
• 3d432d2 Fix issues identified by Psalm
• 7f6a56b Update Psalm
• 4d9527d Merge branch '7.5' into 8.3
• d434b33 Fix issues identified by Psalm
• efb58e3 Merge branch '7.5' into 8.3
• ae2417e Enhancement: Use built-in PHP 7.3 to speed up build for 8.3
• Additional commits viewable in compare view

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

---

Note: This repo was added to Dependabot recently, so you'll receive a maximum of 5 PRs for your first few update runs. Once an update run creates fewer than 5 PRs we'll remove that limit.

You can always request more updates by clicking Bump now in your Dependabot dashboard.

Dependabot commands and options

You can trigger Dependabot actions by commenting on this PR:

• @dependabot rebase will rebase this PR
• @dependabot recreate will recreate this PR, overwriting any edits that have been made to it
• @dependabot merge will merge this PR after your CI passes on it
• @dependabot squash and merge will squash and merge this PR after your CI passes on it
• @dependabot cancel merge will cancel a previously requested merge and block automerging
• @dependabot reopen will reopen this PR if it is closed
• @dependabot close will close this PR and stop Dependabot recreating it. You can achieve the same result by closing it manually
• @dependabot ignore this major version will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this minor version will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)
• @dependabot use these labels will set the current labels as the default for future PRs for this repo and language
• @dependabot use these reviewers will set the current reviewers as the default for future PRs for this repo and language
• @dependabot use these assignees will set the current assignees as the default for future PRs for this repo and language
• @dependabot use this milestone will set the current milestone as the default for future PRs for this repo and language
• @dependabot badge me will comment on this PR with code to add a "Dependabot enabled" badge to your readme

Additionally, you can set the following in your Dependabot dashboard:

• Update frequency (including time of day and day of week)
• Pull request limits (per update run and/or open at any time)
• Out-of-range updates (receive only lockfile updates, if desired)
• Security updates (receive only security updates, if desired)

Finally, you can contact us by mentioning @dependabot.

[welcome]

BOOM! Your first PR with us, thank you so much! Someone will take a look at it shortly.
Please keep in mind that:

• if this constitutes a breaking change, it might take quite a while for this to get merged; we try to emulate the Laravel release cycle as much as possible, so developers can upgrade both software once; this means a new big release every ~6 months;
• even if it's a non-breaking change, it might take a few days/weeks for the PR to get merged; unless it's a no-brainer, we like to have some community feedback on new features, before we merge them; this leads to higher-quality code, in the end; we learnt this the hard way :-)
• not all PRs get merged; sometimes we just have to hold out new features, to keep the packages lean; sometimes we don't include features that only apply to niche use cases;
• we're not perfect; if you think we're wrong, call us out on it; but in a kind way :-) we all make mistakes, best we learn from them and build better software together;

Thank you!
-- Justin Case The Backpack Robot

[dependabot-preview]

Superseded by #78.