Set up Travis-CI testing

[davidlmobley]

I want to enable Travis-CI testing. At the very least it should probably:

• Check that the info in the database is complete
• Check for duplicate molecules
• Check that reading in the mol2/sdf files into OEMols results in the same isomeric SMILES as those corresponding to the "source data"
• Re-make the plots and re-compute the statistics (and check that statistics haven't changed?)

More ambitiously, it could also:

• Rebuild input files (all of them is probably too slow, though this could be flagged as a "slow" test and skipped by Travis-CI; perhaps a test could rebuild some of the input files)
• ...?