Adding new tests to increase coverage

It doesn't make any sense to me that we would need to have `requires_binary` set to True for MegaM files. That flag is meant for things that use `DictWriter` and the `json` library that stubbornly do not support unicode output on Python 2.  

We're just printing stuff to a file, and that should work fine with unicode on Python 2.  I understand that it was crashing, but I'm not convinced this is the correct solution.