Progress bar for long running tasks

I was working on a longer running task, and I thought it might be nice to have a function similar to `capifony_pretty_print`  to give progress indication for file downloads and the like.

I have created wrapper around [ruby-progressbar](https://github.com/jfelchner/ruby-progressbar) and added two new functions: 

`capifony_progress_start` & `capifony_progress_update`

The API for these methods are pretty simple `capifony_progress_start` can be called with a custom message. `capifony_progress_update` takes two self-explanatory arguments `current` and `total`.

If you take a look at [the database tasks](https://github.com/everzet/capifony/blob/master/lib/symfony2/database.rb) I have given an example implementation of the new functions for "database:dump:remote"

Screenshot:

![progress indicator screen shot](http://f.cl.ly/items/2X2z391C0Z1Q0r0m0v3M/capifony-progress-indicator.png)