Fix: Unknown props warning in React 15.2.1, ES6'ize, add sheet caching, better regex for matching selectors

[luigiplr]

PR fixes the following warning when used with React15.2.1

https://fb.me/react-unknown-prop

Other changes include:

• bringing component up to ES6 spec
• New method for assigning default uniqe ID's (namespaces)
• refactoring webpack configuration
• changes to package.json scripts (see readme)
• dependency updates
• prepublish task (babel)
• add sheet caching to prevent un-needed regex parsing
• enhance regex to allow for input attribute selectors

[alexchiri]

I've been noticing these little buggers warnings lately. Would be great to have them go away! :-)

[RickWong]

Thanks guys I will merge this later today.

[willbutler]

@luigiplr I don't think the conflicts are major. Would you mind rebasing your branch onto master so we can get this merged? Thanks!