bug: paired-heatmap top-k-microbes fails when top microbes are not found in ranks

[nbokulich]

Error reported in QIIME 2 forum

The issue is at these lines: https://github.com/biocore/mmvec/blob/ec082d25be946971d203d96e77504aaaa3157cfc/mmvec/heatmap.py#L199-L201

This results in a KeyError if any of the features (microbes) are missing from the ranks table.

either those lines should be amended to grab only features that are present in ranks, or better yet ranks and microbes_table should be subsetted to keep the intersection somewhere before this line: https://github.com/biocore/mmvec/blob/ec082d25be946971d203d96e77504aaaa3157cfc/mmvec/heatmap.py#L175