fix(angular.copy): change angular.copy to correcly clone RegExp

angular.copy previously copied RegExp as an empty object. Change detects
RegExp instance and clones into new RegExp. This change is based on a previous
fix to allow Date to be copied.

Closes angular#3473

Author: AndyHitchman

src/Angular.js

@@ -611,6 +611,8 @@ function copy(source, destination){
         destination = copy(source, []);
       } else if (isDate(source)) {
         destination = new Date(source.getTime());
+      } else if (isRegExp(source)) {
+        destination = new RegExp(source.source);
       } else if (isObject(source)) {
         destination = copy(source, {});
       }

test/AngularSpec.js

@@ -31,6 +31,29 @@ describe('angular', function() {
       expect(copy(date) === date).toBeFalsy();
     });
 
+    it("should copy RegExp", function() {
+      var re = new RegExp(".*");
+      expect(copy(re) instanceof RegExp).toBeTruthy();
+      expect(copy(re).source).toEqual(".*");
+      expect(copy(re) === re).toBeFalsy();
+    });
+
+    it("should copy literal RegExp", function() {
+      var re = /.*/;
+      expect(copy(re) instanceof RegExp).toBeTruthy();
+      expect(copy(re).source).toEqual(".*");
+      expect(copy(re) === re).toBeFalsy();
+    });
+
+    it("should deeply copy literal RegExp", function() {
+      var objWithRegExp = {
+        re: /.*/
+      };
+      expect(copy(objWithRegExp).re instanceof RegExp).toBeTruthy();
+      expect(copy(objWithRegExp).re.source).toEqual(".*");
+      expect(copy(objWithRegExp.re) === objWithRegExp.re).toBeFalsy();
+    });
+
     it("should deeply copy an array into an existing array", function() {
       var src = [1, {name:"value"}];
       var dst = [{key:"v"}];