first pass at some working functionality for the uclust consensus taxon assigner
added some doc on how to use this
adding uclust.py and test_uclust.py to pycogent_backports

we need the --allhits parameter for #1141
updated imports
updated to reflect new to-do
first functional version, pending tests
added test framework for uclust tax assigner - need to make tests pass
added basic tests; changes output of some private methods
added tests, fixed bug
added tests, fixed bug
added tests
added tests, improved handling of unassigned
added test
changed parameter name to better align with other taxon assigners
made UclustConsensusTaxonAssigner accessible on command line
updated parameter name to be more descriptive
added logging of uc file
updated parameter names for clarity
added usage information
added parallel wrapper for uclust taxonomy assigner