Add custom error message to Q.timeout method

q.js

@@ -1334,14 +1334,15 @@ function done(promise, fulfilled, rejected, progress) {
  * some milliseconds time out.
  * @param {Any*} promise
  * @param {Number} milliseconds timeout
+ * @param {String} custom error message (optional)
  * @returns a promise for the resolution of the given promise if it is
  * fulfilled before the timeout, otherwise rejected.
  */
 Q.timeout = timeout;
-function timeout(promise, ms) {
+function timeout(promise, ms, msg) {
     var deferred = defer();
     var timeoutId = setTimeout(function () {
-        deferred.reject(new Error("Timed out after " + ms + " ms"));
+        deferred.reject(new Error(msg || "Timed out after " + ms + " ms"));
     }, ms);
 
     when(promise, function (value) {

spec/q-spec.js

@@ -1583,6 +1583,22 @@ describe("timeout", function () {
 
         return promise;
     });
+
+    it("should reject with a custom timeout error if the promise is too slow and msg was provided", function () {
+        var goodError = new Error("haha!");
+        return Q.delay(100)
+        .timeout(10, "custom")
+        .then(
+            function () {
+                expect(true).toBe(false);
+            },
+            function (error) {
+                expect(/custom/i.test(error.message)).toBe(true);
+            }
+        );
+    });
+
+
 });
 
 describe("delay", function () {