Add coveralls support

[ryan-roemer]

UPDATE: I think this is ready for review.

I'm opening the PR now to make sure Travis + Coveralls build actually works. We can tweak this further if desired...

Fixes #136

• Adds coveralls integration
• Runs tests in Travis
• Adds badges (and moves links to bottom of README)

/cc @alexlande @ianobermiller

[ryan-roemer]

CI is hitting jestjs/jest#266 for Node v0.12 which is now aggregated into jestjs/jest#243 "Update to work with node v 0.12.0"

Disabling travis on 0.12 for now and have ticket #138 to track

> radium@0.11.1 test /home/travis/build/FormidableLabs/radium
> jest
Using Jest CLI v0.4.1
Waiting on 3 tests... FAIL  modules/__tests__/resolve-styles-test.js
Error: Worker process exited before responding! exit code: null, exit signal: SIGSEGV
stderr:

A worker process has quit unexpectedly! This is bad news, shutting down now!

[alexlande]

Thanks @ryan-roemer! This is awesome.