Added builder class (from tbidbaxlipo)
Added debug message to bng.py output
Option to specify output file basename in bng/run_ssa
Left a colon off the if block
Merge remote-tracking branch 'pysb/master'
keep changes to do_export from leaking

The reset of do_export needs to go *after* the model load, not before.
otherwise if the last model to be loaded changes it to False then that
state will leak out into subsequent tests.
keep noisy distutils output from breaking doctests
Merge remote-tracking branch 'pysb/master' into lolab