forced abspath on reference fp
updated docstrings, added more tests
flake8 compliant
removed the 'uclust' from --uclust_similarity and --uclust_min_consensus_fraction in the parallel assign taxonomy scripts to correspond with the changes in scripts/assign_taxonomy.py
Improvements to split_otu_table.py

This PR reduces the code complexity of split_otu_table.py and adds functionality
to allow a user to pass multiple fields to split the biom table on. Adds significant documentation to the library code and the script.
addressed comments
remove unused imports
BUG: Remove extra <tab> character in alpha's HTML

The make_rarefaction_plots.py had an extra <tab> character in between
some of the javascript code that's used to display the plots.

Fixes #1483
_get_consensus_assignment() moved to TaxonAssigner class
merge resolved
Merge pull request #1664 from ElDeveloper/alpha-html

BUG: Remove extra <tab> character in alpha's HTML
Merge branch 'master' of https://github.com/biocore/qiime into sortmerna-assign-taxonomy

pull from upstream
_tax_assignments_to_consensus_assignments now in TaxonAssigner and used by SortMeRNA and Uclust
Merge pull request #1662 from ekopylova/sortmerna-assign-taxonomy

Add sortmerna to assign_taxonomy.py
Merge branch 'master' into split_otu_table_update
Updated ChangeLog.md
Merge pull request #1663 from wdwvt1/split_otu_table_update

Improvements to split_otu_table.py
Add test for write_seqs_to_fastq
Change test to reflect new api

split_fasta_on_sample_ids_to_files got a few new arguments
Change write_seqs_to_fasta; use context manager