WIP: Refactor on top of capistrano v3

Capistrano v3 [was announced][1] in June and has many improvements that allow for capifony to be a much simpler layer on top of some already powerful tools.

v3 is still undergoing development and as such some current features in capifony are not possible however this pull request has implemented the most basic capifony features for deploying a Symfony 2 app and is hopefully a decent enough starting point.

This is a good opportunity to cut some of the cruft from capifony (Symfony 1 and `bin/vendors`) and make it a tool that is a little easier to use and more importantly maintain.

I have written a [changelog][2] that details the changes I have made so far.

[1]: http://www.capistranorb.com/2013/06/01/release-announcement.html
[2]: https://github.com/peterjmit/capifony/blob/capistrano-v3/CHANGELOG%20(v3).md