fixed some typos and an indentation error
Good fast working version of taxon_segregator.py
removed pysam as it was soooooo slow.  Instead rolled my own
SamRead class and used subprocess.call to samtools view for the
binary to text parsing.  Implemented a simple merge function
when segregating such that low ranked taxons like genus or species
will be merged into higher taxons when there is not enough coverage.
However this has a limitation in that if this requires that a new
taxon be generated, it will not be tested as you cannot append to
the list that you are iterating through. May be solved with recursive
algorithm