either-3.4: CHANGELOG.markdown

3.4
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* Delegate `fail` to the underlying `Monad`, rather than `error`.

3.3
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* Inverted roles between `Semigroup` and `Alt`. This let us write `Alternative` and `MonadPlus` instances that are compatible.
* Removed the `Functor` constraint on most instances in exchange for incurring a `Monad` constraint on `Traversable`. `EitherT`
  is after all, a `Monad` transformer first and foremost.

3.2
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* Changed the `Semigroup` to use a `Semigroup` to combine `Left` branches. Left `Alt` untouched, so you can mix and match.

3.1
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* Added instances for `mtl` classes and `MonadRandom`.
* The meaning of `mapEitherT` has changed to match `mapErrorT` in the `mtl`. The old `mapEitherT` is now `bimapEitherT`.

3.0.3
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* Started `CHANGELOG`