Pseudomuto role

# Adding a role for me specifically. 

The _pseudomuto_ role includes the _dev_ role and will:

* Clone/update my dotfiles repo to `node[:pseudomuto][:dotfiles_dir]`
* Ensure the default shell is_zsh_
* Run either `rake` or `rake update` for dotfiles

# Also Introduced in this PR

* Site cookbooks for cookbooks related to roles and other non-community functionality. Added _base_ and _pseudomuto_ site cookbooks so far.
* _Vagrantfile_ updated to look in both cookbooks and site-cookbooks directories for cookbooks.
* Simple config file for knife added so we can use `knife cookbook create [NAME]` to create a new site-cookbook