Replaces embed panel button icon

Adblock blocks `fa-share-alt` ![image](https://cloud.githubusercontent.com/assets/302258/5117822/a658ee8a-700e-11e4-8733-8931a5f552b0.png) icon class, and hides embed functionality. 

Replaced the icon with `fa-code` ![image](https://cloud.githubusercontent.com/assets/302258/5117832/bdf1ae56-700e-11e4-9d18-9ffb60fa95a4.png)

![image](https://cloud.githubusercontent.com/assets/302258/5117895/75a7105e-700f-11e4-8dc9-28c7a59f2aa8.png)