Bump version to 1.1.0.0

Remove no-longer-needed instance for IO. Bump version to 1.0.1.0. Fixes 

#10.

Fixes "overlapping instances" error in clients that use IO exports.

Use closed type families to remove need for `Identity` monad at the e…

…nd of functions. Bump version to 1.0.0.0.

You can now export any pure function of type

  a -> b -> ... -> r

and no longer need to use

  a -> b -> ... -> Identity r

This is what I've been looking forward to ever since GHC 7.6.

Also remove all helpers, wrappers, and support for exporting `... -> Identity r` functions.

Upgrade to msgpack-1.0.0, require GHC 7.10, bump version to 0.2.0.0. F…

…ixes #5.

With msgpack-1.0.0 we unfortunately lost the ability to give clear error
messages; if there is a number-of-arguments mismatch, `unpack` now just
returns `Nothing`.

Also add stack.yaml and update TravisCI config.

Also switch to using `stack` in the README.

Bump version to 0.1.0.2

Bump version to 0.1.0.1