Add coverage (although it doesn't work via tox, have to run manually right now)
Add the start of get_atbats tests, and make get_atbats raise if there are no atbats
Adjust where ParseError is raised from so it makes sense, and test it
Add branch coverage
Remove classes and have a single transform function that takes the attribute dictionary and a dictionary of the proper types.
Test that we don't cover anything up when type conversion goes wrong
s/input/timestamp so we're not using a builtin name
Add _to_datetime tests and add some safety to the implementation