Move form Travis CI to Github Actions

[akosveres]

Description

The PR introduces two workflows:

• build: Build and run tests during pull requests and merge in to master
• publish: On a tag push create a release, build and push assets

Changes to the Makefile:

• Remove ${GOPATH} definition during e2e test setups to accomodate the github actions environment.

Motivation and Context

• I have raised an issue to propose this change this is required

Fixes openfaas/faas#1585

How Has This Been Tested?

Tests have been carried out on my fork:
Build workflow: https://github.com/akosveres/faasd/runs/1360591487?check_suite_focus=true
Publish workflow: https://github.com/akosveres/faasd/runs/1360692301?check_suite_focus=true

The publish workflow was cancelled by mistake, if needed, I can run a successful one.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

Commits:

• I've read the CONTRIBUTION guide
• My commit message has a body and describe how this was tested and why it is required.
• I have signed-off my commits with git commit -s for the Developer Certificate of Origin (DCO)

Code:

• My code follows the code style of this project.
• I have added tests to cover my changes.

Docs:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[alexellis]

Please can you convert to our plugin for this? See alexellis/k3sup for an example of how.

[alexellis]

Approved for merge. Please send a follow-up PR to simplify the upload of assets.

Please also remove create_release.outputs as a reference. We will create each release with the GitHub UI

[alexellis]

Hi @akosveres thank you for your PR. Please see comments for follow-up changes.