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``
This line can be deleted b/c these changes didn't make it into a release (they aren't in 1.8.0).