list cogent and biom-format as dependencies
added Cython dependency
remove Cython installation from travis
Updated installation instructions for #166
be specific about numpy version
use biom-format 1.2.1 and specify URL because its not on PyPI
added a comma
fixed wrong version number for biom-format
update biom-format to 1.3.1 for #167
remove dependency_links for #167
updated install documentation for #167
Merge pull request #167 from audy/install-dependencies

Install dependencies (fixes #166)