Fullscreen toggle

Hey there!
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I was wondering how come the client didn't have a full screen button. Not sure if it was intended or forgotten, but here is the PR in case you guys do want it. The feature is as simple as it sounds.

![enter image description here][1]


  *Top-Right Corner - Shows the full screen toggle button on its normal state*
  
  ![enter image description here][2]
  
  *Top-Right Corner - Shows the full screen toggle button on its hover state*


![enter image description here][3]

*Komanda running full screen on a 1080p monitor with the mouse touching the top corner to display the OS X tool bar*


  [1]: http://puu.sh/9KrkG/03b5f8d2dd.png
  [2]: http://puu.sh/9KrrE/6ceb063c27.png
  [3]: http://puu.sh/9Krw9/6965b3693e.png
  
  **Functionality has only been tested on OS X. It is suggested that it is checked on Windows and Linux before merging this PR.**
  
  Cheers!