chore: Add current Go versions to Travis

[pangaunn]

Fixes

Checklist

• I confirm that the latest PR commit passes its Travis CI build
• 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 current Go versions to Travis

If you have questions, please send an email to Twilio SendGrid, or file a Github Issue in this repository.

[codecov]

Codecov Report

Merging #372 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #372   +/-   ##
=======================================
  Coverage   72.47%   72.47%           
=======================================
  Files           3        3           
  Lines         476      476           
=======================================
  Hits          345      345           
  Misses        127      127           
  Partials        4        4

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[thinkingserious]

Hello @pangaunn,

Thanks again for the PR!

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

Team SendGrid DX