Huge API refactorings, add webpack loader

- Add webpack loader (works with extract-text-webpack-loader).
- Remove Transformer modules, provide instead `transform(ast, filename)` and
  `transformString(string, filename)` functions.
- Remove CLI utility.
- Some function renamings.
- Provide `styles` prop for React.DOM.* instead of patching `style` behaviour.
Merge pull request #12 from andreypopp/webpack

Webpack integration - will do some extra fixing to make sure the example works out of the box