Sourcemap paths

![tumblr_mde5kxekvf1rhfw98o1_400](https://cloud.githubusercontent.com/assets/925735/3421995/8532955a-ff0f-11e3-81de-857f802bddf5.gif)

Fixes #17 and #49 and all those other #$&*&^%$ sourcemap issues. Sourcemaps point to the original files on disk. No extra settigs necessary.

A little addition to gulp-intermediate made this easy.
error should be emitted

```
this.emit('error', new gutil.PluginError
```

though this must be the this in the stream context.