gabrielecirulli/2048 — pull request #63 by azeff (2014-03-16 19:40:46+00:00)
Title: Undo

Use **meta/ctrl + z** or **u** key to undo.
For small screens that presumably represent smartphones show 'undo' button.
![2014-03-16 23 36 21](https://f.cloud.github.com/assets/152304/2431770/6ee498da-ad42-11e3-86a5-b22f0011e7ba.png)