Config syntax

This change allows the user to specify multiple file patterns including exclude patterns in their Gruntfile, including files that come from different directories, by using the syntax described in the Grunt documentation [here](http://gruntjs.com/configuring-tasks#files).

This allows me to build my application including the dist directory but excluding the unminimized scripts, documentation files, and other unnecessary stuff in bower_components for a savings of 11MB on the resulting node-webkit executables.

However, as you can see in the examples that this changes the configuration syntax. This is not backwards compatible (but could maybe be made so). Users with the old configuration syntax will get a message telling them that there's a file with multiple sources (and the sources listed will be every file that was previously included into the zip).