Hi,

For a packager (like me :) ) it's useful to have full list of dependencies and also what we need to run tests (and how).

There is some discrepancies between https://github.com/blaze/dask#dependencies and http://dask.pydata.org/en/latest/install.html

For the unittests, it seems that we need python-pygraphviz and python-cachey

Thanks!