Trial to apply GitHub Action instead of TravisCI

[parroty]

Summary

• Apply GitHub Action instead of TravisCI for more smooth integration with GitHub.
  • Revisit of Github Actions for excoveralls repository fail #211

Changes

• Fix test codes
  • Enforce to revert GitHub related environment variables after unit test running.
  • Remove escape characters (color related) checks in test assertion (for avoiding unexpected errors in tests in GitHub action).
  • Update mock version.