Tokenizes CSS source
@param {String} source
@returns {Array}
function(source) {
        	// transform tokens
	 		var pos = 0;
	 		return _.map(this.lex(source), function(token) {
	 			if (token.type == 'line') {
	 				token.value = getNewline(source, pos);
	 			}
	 			
	 			return {
	 				type: token.type,
	 				start: pos,
	 				end: (pos += token.value.length)
	 			};
			});
		}