refactoring into a distinct binary and library

[etnbrd]

I put everything in lib, and did some refactoring, mainly to remove every console.log.
Instead, a callback receives errors, and status code from the response.

I also modified the readme, and added a few tests.

[mgcrea]

👍 Do need this to integrate code climate in my gulp workflow.

[Xiphe]

👍 this approach seems to be much cleaner to me.

Pretty wired that the codeclimate-test-reporter npm module is not consumable as a library in other node projects.

[avdg]

I guess that I'll resolve this merge conflict