Adding a few tests which I would expect to succeed?

Frank, I've added a few tests, two of which fail -- but I would have expected
(based on the code, as I read it) to succeed.  If you don't think they should succeed,
can you add some comments to that effect on the relevant methods?
Added a second IAE-generating test on an incorrect 'find'
Merge pull request #2 from genomebridge/prefix-trie

Adding a few tests which I would expect to succeed?