Update ubuntu install script

[ValarDragon]

• Targeted PR against correct branch (see CONTRIBUTING.md)

• Updated relevant documentation (docs/) - this is the docs

• Added entries in PENDING.md with issue # - updating docs doesn't require this

• rereviewed Files changed in the github PR explorer

---

For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Merging #2803 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           develop   #2803   +/-   ##
=======================================
  Coverage     56.6%   56.6%           
=======================================
  Files          156     156           
  Lines         9836    9836           
=======================================
  Hits          5568    5568           
  Misses        3888    3888           
  Partials       380     380

[cwgoes]

A few comments, also needs a PENDING.md entry. Haven't tested the script yet, will test after revisions.

[ValarDragon]

This script is part of updating the docs, I really don't think it should have a changelog entry.

[zramsay]

just tested on fresh DO instance (w/ latest commit)

[cwgoes]

Tested on Ubuntu 18.04 (Docker).