fixed multiline comments

fixed webpack#62
(. doesn't match newline)

Author: sokra

lib/parseSource.js

@@ -186,7 +186,7 @@ function extendsFromMatch(match, request) {
 var parser = new Parser({
 	// shared stuff
 	comments: {
-		"/\\*.*?\\*/": true
+		"/\\*[\\s\\S]*?\\*/": true
 	},
 	strings: {
 		'"([^\\\\"]|\\\\.)*"': true,

test/moduleTestCases/comments/expected.css

@@ -0,0 +1,11 @@
+/*
+ * a ' above
+ */
+
+._bg_ {
+  background-image: url({bg.jpg});
+}
+
+/*
+ * a ' below
+ */

test/moduleTestCases/comments/source.css

@@ -0,0 +1,11 @@
+/*
+ * a ' above
+ */
+
+.bg {
+  background-image: url(bg.jpg);
+}
+
+/*
+ * a ' below
+ */