Add a root CWD to all commands that do not require something specific

Causes each of these commands to be run from `/`
Install wp-cli from /home/vagrant/

We symlink the `wp` file from `/home/vagrant/`, so we should make sure the installer runs there as well, even though it likely doesn't matter a whole bunch
WSUWP Platform should be cloned into /var/www/

Removes the manual directory change that we included as part of the command before.
Setup slightly smarter working directories for production commands
Merge pull request #9 from washingtonstateuniversity/9-cwd-fix

A proper current working directory should be specified for commands run