Improve `ffetch` usability

Hi @Gkolocsar, @gastonmancini, @matiasbeckerle and @jfazzini,

I have improved `ffetch` in order to avoid some of the restrictions and side effects. Now it only works as a kind of `fetch` including our `tfs` branches (qa, integration, default) to mitigate git-tfs bug.

You can see the changes on README.me to easily see how it has been improved.

Please, review it, then I will merge it and you can update your clones to enjoy the enhancements.