curried Either and added Left and Right

properties are prepended with _ to allow functions left() and right()
isRight() added to pass strict mode

> isn't it a better idea to fork the monads from one of the other repos

i've had the same thought. i implemented the types a while ago because i wanted to learn them.

as you point out, the only advantage to rolling our own at this point is a curried either constructor, but that would pretty easy to implement on top of an existing impl, either as a fork or as a wrapper.