update dependencies in setup.py

fixes #1719 

A couple of notes:
 * removed the one dependency on ``future`` since we're not shooting for py2/py3 compatibility in QIIME 1.9.0
 * made the ``burrito`` dependency the same as for ``burrito-fillings``
There's also a mention in this file that HDF5/h5py are required dependencies -- can that be removed?