Split databaseTest into separate tests by reaction family.
Split databaseTest into separate tests by reaction family.

It uses test generators, a feature of nose, which means we
can't use the built-in unittest module any more, but that's OK
because we were using nose anyway.  You can use nosetests, or 
just run it on its own:

 $ python databaseTest.py
nickvandewiele/RMG-Py,nyee/RMG-Py,chatelak/RMG-Py,enochd/RMG-Py,KEHANG/RMG-Py,faribas/RMG-Py,chatelak/RMG-Py,pierrelb/RMG-Py,faribas/RMG-Py,nickvandewiele/RMG-Py,KEHANG/RMG-Py,comocheng/RMG-Py,nyee/RMG-Py,pierrelb/RMG-Py,comocheng/RMG-Py,enochd/RMG-Py