Pass file information (name/mode) along to transform functions.

**Why**: This is useful for times when you want dynamically transform files based on the type of file associated with the stream.  

For example:
 - You're copying a file hierarchy, to instrument javascript files for code code coverage analysis, without excluding other files that contain metadata (json, etc.)
 - You're copying a file hierarchy, to compress image files for production usage.

**Testing**: I've added a vows test to make sure the file information is passed on properly.