map barcodes: no reverse complement
refactored intersect
small doc improvements
refactored derep_fulllength

The original script apparently had some functionality for a "uc" file.
This file showed the read IDs that mapped to the each sequence:

ACGT  foo    bar    baz
CATC  lorem  ipsum  qualcum

This doesn't seem to appear in downstream analysis, so I dropped it from
the refactored script.
config: added gold line
otu caller: mostly whitespace movements
otu caller: refactored comments into docstrings
usearch: added __init__ for easy importing
moved fasta_entries to util
tests: initial commit
tests: cleans up tests folder
tests: renamed
tests: added hashbang