code: function extract(sources, options) {
  		return sources
  			.map(function(src) {
  				return [src, grunt.file.read(src)];
  			})
  			.filter(function(list) {
  				return syntax.valid(grunt, list[0], list[1]);
  			})
  			.map(function(list) {
  				return extras(list[0], list[1], options);
  			});
  	}
docs: Extract content from files and
  parse through various options.
  @param {Array<string>} sources
  @param {object} options
  @returns {Array<string>}