Vagrant support

Added `Vagrant` support to the unidata-python-workshop project.  This will allow a user to check out the workshop materials from github and then, from the workshop directory, use vagrant to create a VM configured with Anaconda, iPython notebook and other tools for the workshop.  Any changes made to the ipython notebooks from within the VM will persist on the host machine, as they are stored in the unidata-python-workshop directory.

See the file `VAGRANT_README.md` for full instructions on creating and using Vagrant with the workshop materials.