Feature/git support

Hi Ronnix,

  Here is a little suggestion/starter to manage repository. It offers basic functions to clone, update or reset a repositiory. 

Here are some remarks/questions:

* When error occurs, like Control Version System is not supported, it just prints a red message. Would you prefer that it raises an exception ?
* It deals only with Git repositories.
* How can I write Fabtools tests ? Actual test files are not very explicit.

Let me know if you're ok with this implementation. It's very basic but it should be enough for most of the usages (unless you don't use Git).