clean up the hash generation so it's generally useful.
Add the private id/hash systems and a bunch of tests for them; still needs a bit of work
make tests run properly
remove some debugging code
Make it jshint-clean.
Merge pull request #25 from tidepool-org/kjq/privateidhash

I'm going to merge this myself because it's saturday and the tests have made me pretty confident, plus I want to do other things (like merge to master).