added prep notebook for sortmerna
updated to use new sortmerna tax assigner
containing partial output
updated to also sweep over --num_alignments settings
updated to use pre-computed index, much faster...
added new sortmerna results
added uclust and usearch results, and updated so query results can be in multiple top-level directories
Merge pull request #58 from gregcaporaso/add-sortmerna

adding sortmerna comparison notebooks