Support aeson 0.11

[agrafix]

See commercialhaskell/stackage#1211

@bartavelle , would you like to give this a shot?

[bartavelle]

I'll make it compile but I won't be able to try the end-to-end tests for the next 10 days.

[bartavelle]

The compilation issue should be fixed with the latest patch. There probably will be a bug if someone tries to play with the new unwrapUnaryRecords option. I will fix the code when I'll have access to my main computer.