introduces the sourceMap changes from #19 and adds a  sourceMayRoot

I'm sorry this has introduced so many commits many of which are me reverting changes I made and pushed to my repository, but this introduces 2 changes
1) the changes made by @timvanelsloo that fixed sourceMaps has been introduced with changes made to the coffeescript file and the generated js file.
2) added a new option called sourceMapRoot that adds a root the location of the sourceMap.

I had originally introduced 2 different options to do the same thing
 i) inspectPrefix which would make sure the middleware only kicked in when the pathname to the js matched a specific prefix
ii) replacePrefix which would remove the prefix but add it back to the path to the sourceMap.
However, I realised that a lot of this can be accomplished automatically with expressjs since the first parameter to the `use` method of an express app is a static mount point. sourceMapRoot helps adjust the url exposed to the user