New code editor : ACE

Hi.

He is my [ACE](http://ace.ajax.org/) directive for AngularUI.

I drop my last implementation : 
```html
<ui-ace mode="css " onchange="changeInfo" show-gutter use-wrap-mode  ng-model="input"></ui-ace>
```
for a more common way :
```html
<div ui-ace="{mode:'css', onChange: changeInfo, showGutter:true, useWrapMode:true}" ng-model="input" ></div>
```