Exclude examples from go tests, Travis Job

[anchepiece]

Fixes #244

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:

Hello 👋,
Thanks sendgrid team for releasing and continually improving this library.

This is a minor fix that excludes code that shouldn't be tested in the examples, vendor, and docker directories.

[SendGridDX]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #273 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #273   +/-   ##
=======================================
  Coverage   70.95%   70.95%           
=======================================
  Files           3        3           
  Lines         451      451           
=======================================
  Hits          320      320           
  Misses        127      127           
  Partials        4        4

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[thinkingserious]

Hello @anchepiece,

Thanks again for the PR!

It's HACKTOBERFEST! We want to show our appreciation by sending you some special Hacktoberfest swag. If you have not already, could you please fill out this form so we can send it to you? Thanks!

Team SendGrid DX