Changes and additions from ASTRAL 2.03 to 2.04:

* BLAST version

In constructing representative subsets, we changed the version of
BLAST used from 2.0.9 to 2.2.18.  We try to use the same version
of BLAST from one ASTRAL release to the next in order to improve
consistency, but 2.0.9 no longer runs on our current hardware.