Vagrant plugin update

The current version of the script works well for vagrant <1.0.X

The support for vagrant 1.1 is ready but commits need to be merged in the python-vagrant upstream module.

Add:
- CPU count support
  - RAM support (add option name --ram duplicates --memory kept for legacy)
  - name support (so the vagrant name becomes the VBox name)
  - IP support; IPs are incremented by one for each box count
  - Version; Vagrantfile format (default 1) - support Vagrantfile format 1 and 2.

Notes:
  - only support virtualbox provider - no other providers at the moment.
  - python-vagrant is still used, we most likely want to drop it later on if no maintainance is performed upstream...
  - If you are using Vagrant >1.1, you must use Vagrantfile format v2; python-vagrant is only currently able to handle properly Vagrantfile v1 due to some bad regex in the command output parsing...

To enable vagrant 1.1 support, need to install the patched version of python-vagrant:

```
sudo pip install  git+git://github.com/zbal/python-vagrant.git#egg=python-vagrant
```