Added support for non-flattened output

Hi,

Please accept support for non-flattened output.  The changes add support for keeping the full directory structure in the output and also updates paths in hash map to reflect full paths.  Also, added a base bath for the source.

Ex new config object:


grunt.initConfig({
	hash: {
		src: 'examples/*.js',  //all your js that needs a hash appended to it
		basePath: 'static/', //base path of your src
        flatten: false, // wether or not to flatten the output - default is true
		mapping: 'examples/assets.json', //mapping file so your server can serve the right files
		dest: 'examples/dist/' //where the new files will be created
	}
});