Add CodeCov support to .travis.yml #109

[scomert]

Closes #109
Waiting for review. Thanks.

[SendGridDX]

Thank you for your submission, we really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[mbernier]

We were not able to merge this PR for two reasons:

1. Update .travis.yml #112 beat you to it
2. You did not sign the CLA

We would still love to chat with you! If you are interested, we would love the opportunity to talk to you about Hacktoberfest and our API libraries.

Our agenda would be: Explore what you liked and is there anything we can do to improve?

You can grab a time on my calendar that works for you and we can have a chat on Google Hangout or Skype. If you prefer, you can email me using my GitHub username at my company’s domain.

Thank you so much,

Matt Bernier - @mbernier - SendGrid Developer Experience Product Manager
Elmer Thomas - @thinkingserious - SendGrid Developer Experience Engineer
@sendgrid