add revised phosim driver script
script to convert VizieR catalogs to astrometry.net index files for use with LSST stack
don't resolve absolute path to extraCommands since it may have a default value of 'none'
use backport of OrderedDict if python version < 2.7
Merge pull request #20 from jchiang87/master

refactored phosim.py script and script to make index files for astrometry.net