vmware_fusion support

Adds support for Vmware fusion.

The base box was changed from ubuntu to chef, because ubuntu only provides Virtualbox boxes. Chef's boxes are built from opensource Packer templates, which can be found here: https://github.com/opscode/bento/blob/master/packer/ubuntu-14.04-amd64.json

New build instructions:
```
vagrant box add chef/ubuntu-14.04 --provider=virtualbox OR vmware_fusion
vagrant up
```