ADD support for kit epochs file

Not ready to merge yet.

Things to do:
- [ ] find better way to reshape data in _read_segment
- [ ] add test data
 
Actually, it looks like the data are stored internally with `nchan` iterating slowest, then `nepochs`, then `ntimes` (iterating fastest). So you'll have to do a `.transpose()` *somewhere* (probably in the last step), but in the meantime you can at least get rid of some `.T`'s along the way.