chore: [Closes #55] Add code coverage reporting to CC

[lauratpa]

This PR add code coverage reporting and integrates it with code climate.

Closes #55

Checklist

• I have made a material change to the repo (functionality, testing, spelling, grammar)
• I have read the [Contribution Guide] and my PR follows them.
• I updated my branch with the master branch.
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation about the functionality in the appropriate .md file
• I have added in line documentation to the code I modified

Short description of what this PR does:

Add code coverage and integration to Code Climate

[SendGridDX]

All committers have signed the CLA.

[lauratpa]

For this PR to work on CI, a maintainer (who has access to cc) needs to add the TEST REPORT ID for this repo in code climate to be available as an environment variable in TRAVIS (CC_TEST_REPORT_ID).

https://docs.codeclimate.com/docs/finding-your-test-coverage-token
https://docs.travis-ci.com/user/environment-variables/#Defining-Variables-in-Repository-Settings

[mbernier]

I added the variable to the Travis build and asked Travis nicely to rebuild! Let's see what happens.

[thinkingserious]

Hello @jekuta,

Thanks again for the PR!

We appreciate your contribution and look forward to continued collaboration. Thanks!

Team SendGrid DX