structured-haskell-mode integration

[Pitometsu]

It's a feature request: add support for the structured-haskell-mode to provide common smartparens key bindings and familiar behaviour for Haskell mode.

[Fuco1]

I think this is a valid idea and might be useful for some people. Thanks for bringing it up to our attention.

I'm not against having this in SP per se but it is something I'm not very interested in doing personally. I would accept a pull request if someone is willing to work on this.

I haven't used structured haskell mode so I can't rightly judge if this is going to be a huge win or a small win and for how much effort.