Integrate ZeroClipboard to easily copy code snippets

**What I am trying to solve?**

Usually people will copy the code snippets from Bootstrap documentation and edit according to their need. For bigger section of snippets on selecting the code, page scrolls and unwanted texts are selected which makes copying process little bit complex. To overcome the difficulty and to easily copy the code snippets I have integrated the https://github.com/zeroclipboard/zeroclipboard.

Its not the final implementation. I just wanted to hear the comments from code team.
  * Whether it will be useful?
  * Any mistakes in current code in terms of standard and functionality?
  * etc

If the core team gives me a green signal I will try to implement the tooltip and notification on copy through tooltip.

For demonstration purpose I have added the copy to clipboard in few places of the documentation. Also I have attached the few screenshots for the core team review.

**Browser Suport**
Even though the library depends on the Flash it gives better browser support. Please refer https://github.com/zeroclipboard/zeroclipboard#support for browser support.

**Screenshots**

![copy-to-clipboard-highlight](https://f.cloud.github.com/assets/528129/1810600/9559a8fc-6e2c-11e3-945f-65ae2dd27b37.png)

![copy-to-clipboard-bs-example-and-highlight](https://f.cloud.github.com/assets/528129/1810592/311631e4-6e2c-11e3-8ac2-f2b1ec6ca935.png)

![copy-to-clipboard-mobile](https://f.cloud.github.com/assets/528129/1810593/379400dc-6e2c-11e3-97eb-ed119e5287d8.png)