fix(ngResource): correct leading slash removal.

Fixed an issues with ngResource param substitution where it was incorrectly removing leading slash when param was followed by a non-slash character.
Ex:
'/:foo/:bar.baz/:aux'

params = {
  foo: 'aaa',
  bar: undefined,
  aux: undefined
}

The above params were incorrectly producing '/aaa.baz' but now it results in '/aaa/.baz'.

Author: pavelgj

src/ngResource/resource.js

@@ -311,7 +311,14 @@ angular.module('ngResource', ['ng']).
             encodedVal = encodeUriSegment(val);
             url = url.replace(new RegExp(":" + urlParam + "(\\W)", "g"), encodedVal + "$1");
           } else {
-            url = url.replace(new RegExp("/?:" + urlParam + "(\\W)", "g"), '$1');
+            url = url.replace(new RegExp("(\/?):" + urlParam + "(\\W)", "g"), function(match,
+                leadingSlashes, tail) {
+              if (tail.charAt(0) == '/') {
+                return tail;
+              } else {
+                return leadingSlashes + tail;
+              }
+            });
           }
         });
         url = url.replace(/\/?#$/, '');

test/ngResource/resourceSpec.js

@@ -73,6 +73,31 @@ describe("resource", function() {
     R.get({a:6, b:7, c:8});
   });
 
+  it('should not ignore leading slashes of undefinend parameters that have non-slash trailing sequence', function() {
+    var R = $resource('/Path/:a.foo/:b.bar/:c.baz');
+
+    $httpBackend.when('GET', '/Path/.foo/.bar/.baz').respond('{}');
+    $httpBackend.when('GET', '/Path/0.foo/.bar/.baz').respond('{}');
+    $httpBackend.when('GET', '/Path/false.foo/.bar/.baz').respond('{}');
+    $httpBackend.when('GET', '/Path/.foo/.bar/.baz').respond('{}');
+    $httpBackend.when('GET', '/Path/.foo/.bar/.baz').respond('{}');
+    $httpBackend.when('GET', '/Path/1.foo/.bar/.baz').respond('{}');
+    $httpBackend.when('GET', '/Path/2.foo/3.bar/.baz').respond('{}');
+    $httpBackend.when('GET', '/Path/4.foo/.bar/5.baz').respond('{}');
+    $httpBackend.when('GET', '/Path/6.foo/7.bar/8.baz').respond('{}');
+
+    R.get({});
+    R.get({a:0});
+    R.get({a:false});
+    R.get({a:null});
+    R.get({a:undefined});
+    R.get({a:''});
+    R.get({a:1});
+    R.get({a:2, b:3});
+    R.get({a:4, c:5});
+    R.get({a:6, b:7, c:8});
+  });
+
 
   it('should support escaping colons in url template', function() {
     var R = $resource('http://localhost\\:8080/Path/:a/\\:stillPath/:b');