Garnet integration test

[agitter]

This pull request adds a Garnet integration test. It runs Garnet on FOXA1 ChIP-seq data and the a549 example expression data and compares the output files to a set of expected output files.

In order to make the Garnet output reproducible on different machines, I also made two changes to Garnet's motif_regression.py:

• The paths to the motif gifs are now relative to the output directory instead of absolute
• The Garnet output table is now sorted in a stable manner, first by rounded p-value, then by rounded slope, then by motif id.

If we don't like using relative paths for the gifs, I would recommend we add an option to copy the gifs used in the output HTML file into the output directory. That would make the output files portable in the sense that they could be copied to different directories or different machines.

[AmandaKedaigle]

Thanks for the work on this, @agitter! I'm fine with relative paths for the gifs, and stable sorting is great.