Pickle

So this is a further modification of #62, where I've used cPickle to replace our manual "unit munging" code for saving the options in the netCDF file.  

The advantage here is that we don't have to manually guess a bunch of object types and process them manually, we just pickle everything as strings.  

There is the downside of human readability, but IMHO that wasn't actually buying us very much, as we still have an in-memory dictionary representation.