Package nbref with a setup.py script

[wfspotz]

Tasks:

• Write a setup.py script for packaging nbref
• Make sure setup.py installs the CSL files
• Test that the setup.py script works

[wfspotz]

@mpacer, would you be willing to review what is here and see if it matches what you were expecting? The setup.py script does not yet install the CSL files ... I'm looking at how to do that.

[wfspotz]

@mpacer will you be able to help with this?