improve W005 checker by properly parsing URL and checking filename

CC: @hnrch02 
For the future: Files in node don't need to be wrapped in an IIFE node does that for you: https://github.com/joyent/node/blob/cfcb1de130867197cbc9c6012b7e84e08e53d032/src/node.js#L792-L795. And Browserify too.