Modifying exclude_seqs_by_blast.py in order to store the output in a folder.
improved convert_fastaqual_fastq library code

made conversion from fasta + qual -> fastq more readable and
less confusing
further streamlined both directions of conversion
Replaced tests for certain errors

Rather than modify the test code, decided to leave in some "quality
assurance" tests
Removed some line continuations, added file naming function
Added buffering system for multiple file output
Added a tests: utility function, multiple output files

also did a little cleanup (could probably use more)
added functions to access test data

this is the data derived for issue #582. these functions provide access to data as dict of filepaths or dict of file-like objects (lists of lines). because the files are written with the tempfile module, they are automatically cleaned up.
updated documentation
removed debugging statement
moved run_core_qiime_analyses function to new file

additionally began re-factoring to address #477.
added basic unit tests, more will follow
added generation of taxa plots
added category-specific taxa plots
added distance boxplots by category
added compare_alpha_diversity.py on per-category basis.
added test without category data
updated script to new core analysis function
updates to script
added placeholder test to fail on missing tree