feat($resource): support an unescaped URL port

The colon character is used to identify parameters in $resource.
This meant that we had to escape the colon used in a port.
It turns out that this is not necessary if we assume that parameter
names cannot consist of only digits.
If the parameter consists only of numbers, then it's a port.

Closes #2778

src/ngResource/resource.js

@@ -31,8 +31,7 @@
  *
  * @param {string} url A parametrized URL template with parameters prefixed by `:` as in
  *   `/user/:username`. If you are using a URL with a port number (e.g.
- *   `http://example.com:8080/api`), you'll need to escape the colon character before the port
- *   number, like this: `$resource('http://example.com\\:8080/api')`.
+ *   `http://example.com:8080/api`), it will be respected.
  *
  *   If you are using a url with a suffix, just add the suffix, like this:
  *   `$resource('http://example.com/resource.json')` or `$resource('http://example.com/:id.json')
@@ -345,7 +344,7 @@ angular.module('ngResource', ['ng']).
 
         var urlParams = self.urlParams = {};
         forEach(url.split(/\W/), function(param){
-          if (param && (new RegExp("(^|[^\\\\]):" + param + "(\\W|$)").test(url))) {
+          if (!(new RegExp("^\\d+$").test(param)) && param && (new RegExp("(^|[^\\\\]):" + param + "(\\W|$)").test(url))) {
               urlParams[param] = true;
           }
         });

test/ngResource/resourceSpec.js

@@ -106,6 +106,13 @@ describe("resource", function() {
     R.get({a: 'foo', b: 'bar'});
   });
 
+  it('should support an unescaped url', function() {
+    var R = $resource('http://localhost:8080/Path/:a');
+
+    $httpBackend.expect('GET', 'http://localhost:8080/Path/foo').respond();
+    R.get({a: 'foo'});
+  });
+
 
   it('should correctly encode url params', function() {
     var R = $resource('/Path/:a');