Include version to header comment

I think it is useful that version is kept after minify.
If this PR is acceptable, I sent the same PR to ember-data and ember-dev as soon as possible :smile: 

---

Before:

```
/*!
 * @overview  Ember - JavaScript Application Framework
 * @copyright Copyright 2011-2013 Tilde Inc. and contributors
 *            Portions Copyright 2006-2011 Strobe Inc.
 *            Portions Copyright 2008-2011 Apple Inc. All rights reserved.
 * @license   Licensed under MIT license
 *            See https://raw.github.com/emberjs/ember.js/master/LICENSE
 */


 // Version: 1.4.0-beta.1+canary.011b67b8
```

After:
```
/*!
 * @overview  Ember - JavaScript Application Framework
 * @copyright Copyright 2011-2013 Tilde Inc. and contributors
 *            Portions Copyright 2006-2011 Strobe Inc.
 *            Portions Copyright 2008-2011 Apple Inc. All rights reserved.
 * @license   Licensed under MIT license
 *            See https://raw.github.com/emberjs/ember.js/master/LICENSE
 * @version   1.4.0-beta.1+canary.922cd4ef
 */
```

If this PR is acceptable, I sent the same PR to ember-data and ember-dev as soon as possible!