feat(element) element.all exports an 'each' method

Usage:
```
element.all(by.model('foo')).each(function(webElement) {
  // Do stuff with webElement.
});
```
Closes #298

lib/protractor.js

@@ -131,6 +131,14 @@ var buildElementHelper = function(ptor) {
       return ptor.findElements(locator).then(fn);
     };
 
+    elementArrayFinder.each = function(fn) {
+      ptor.findElements(locator).then(function(arr) {
+        arr.forEach(function(webElem) {
+          fn(webElem);
+        });
+      });
+    };
+
     return elementArrayFinder;
   }
 

spec/basic/findelements_spec.js

@@ -362,6 +362,13 @@ describe('global element function', function() {
     expect(colorList.last(0).getAttribute('value')).toEqual('red');
   });
 
+  it('should perform an action on each element in an array', function() {
+    var colorList = element.all(by.model('color'));
+    colorList.each(function(colorElement) {
+      expect(colorElement.getText()).not.toEqual('purple');
+    });
+  });
+
   it('should export an isPresent helper', function() {
     expect(element(by.binding('greet')).isPresent()).toBe(true);
     expect(element(by.binding('nopenopenope')).isPresent()).toBe(false);