Send filename to plugins

[boopathi]

plugin:

...
   Class(path, state) {
     console.log(state.file.opts.filename); // logs `unknown`
   }
...

Babel transform has options - filename and filenameRelative that could be passed in - http://babeljs.io/docs/usage/api/#options

[eventualbuddha]

Fixed in v1.1.3.