Provide a Vagrant development environment

Hey Bharat,

Is there any interest in providing the Gallery community a preconfigured
Vagrant box to make it easier for people to start hacking?

If so, I'll be happy to do what it takes to make this part of the Gallery
infrastructure (e.g. update documentation, build scripts, etc.) and also to
maintain it.

The VM has been created from a Debian 6.0.6 netinst image using this Chef
cookbook:

https://github.com/jozefs/gallery3-cookbook

The cookbook would probably need to be put among the official Gallery
repositories and we'd need to find some space to host the VM (it's currently
hosted on my Google Drive as a proof-of-concept).

As I was unable to figure out how to get a direct download URL from Google
Drive, to test it out, you'll need to manually save the following somewhere on
you computer:

https://docs.google.com/file/d/0B_n9-qOdaaOLLW5GR2tZenlGWVU/edit?usp=sharing

Then import it to Vagrant:

```
 $ vagrant box add 'gallery3dev' /path/to/downloaded/gallery3dev.box
```
Of course, Vagrant and VirtualBox also need to be installed. After this, just
follow the instructions from the commit message.

The cool thing is that this should work across Linux, Mac and Windows.

 - Jozef