get rid of nose

[MeggyCal]

As nose is unmaintained for a while, let us replace it with unittest.

[MeggyCal]

... and tests don't work, because I don't know how to setup your environment :( would you help me with that, please?

[erikbern]

Thanks for the PR! I think it fails because of something with how python setup.py nosetests builds the library before it runs the test. You might have to add a separate step to build the module first. I can clone and take a look.