add propTypes to improve reusability

It's recommended by React:
http://facebook.github.io/react/docs/reusable-components.html
fix syntax error
fix test path
fix jest thinking preprocessor.js was a test file
fix heart component require inside tests
replace Makefile with npm run

Now the bundle script runs a local copy of the stylus and browserify
executables. Much better to mantain everyone using the same version of
stylus and browserify.
fix missing commas
update bundled heart.js
fix animation propType
Merge pull request #1 from hugobessaa/feature/propTypes

Add propTypes to improve reusability