Update .travis config to fix Code Climate settings

Hi! It looks like you have been trying to setup Code Climate coverage reports for your repository and have been having trouble. Sorry about that!

This PR uses the `curl` style test coverage reporting and removes some of the extra config from your `.travis.yml` (like the `addons` section) that is not required. It also removes your repo token from the call. Generally, we don't recommend you add those tokens to open source repos as someone would be able to copy the token and use it to post coverage to your repo on Code Climate.  Instead, you should add the token to an Environment Variable in the repo settings on Travis directly.

Also, the token in your existing config is not the right token. To get the test coverage token, go to https://codeclimate.com, click on the settings link (with the gear) next to your repo. Then click on Test Coverage on the left. From there you should be able to see the right token.

Let me know if you need any help getting setup!