Allow post-transforms to take in options
Pass actual asset object into a second parameter to Transformer's shouldTransform method
Add a 'transformInfo' object to Asset so that data/flags can be stored about an asset as it goes through the pipeline
Also pass asset object as second parameter to Transformer's transformedFileName method.
Some minor JSX transformer improvements

Allow plain '.js' files that contain the /** @jsx React.DOM */ pragma to be transformed
For '.js.jsx' files, add the jsx pragma as the first line of the file if it is missing