transformers: remove instance MonadFix ExceptT and ErrorT

[Bertram Felgenhauer]

David Feuer wrote:
> On Aug 12, 2014 7:50 PM, "Bertram Felgenhauer" <
> bertram.felgenhauer at googlemail.com> wrote:
> > I tend to agree that those MonadFix instances are not immensely useful.
> 
> From my perspective as a generally ignorant person, I think these should be
> kept as long as
> 
> 1. They satisfy the required laws and
> 2. No more useful instances can be written.

I agree completely, and I never wanted to remove the instances.

Cheers,

Bertram