MonadError type class, \/ implementation, tests.
EitherT implementation.
LazyEither implementation.
LazyEitherT implementation.
Task implementation.
Remove redundant test.
MonadError syntax.
Readd BooleanOps Unicode operators

Fix #482.
Merge pull request #748 from hgiddens/monad-error

Monad error
remove `→` (collides with standard library)
Merge pull request #754

Readd BooleanOps Unicode operators