added copy to clipboard option

Fixes #325 
Bootstrap 3 doesn't have a 'share' glyphicon, so used the link icon. 

![clipboard](https://f.cloud.github.com/assets/3893573/2458211/3bc7de3c-af48-11e3-8887-3d530098bfa1.png)
![clipboarddone](https://f.cloud.github.com/assets/3893573/2458213/461dffba-af48-11e3-93ef-17e065ea4366.png)

Implemented using [ZeroClipboard](https://github.com/zeroclipboard/zeroclipboard).