Updating Needle to build on recent stackage LTS

[sordina]

Hello ScrambledEggsOnToast,

I've been playing with Mealy machines lately and thought it would be fun to use Needle in conjunction with the Arrow instance in order to program in ascii art. Unfortunately Needle doesn't seem to build against recent libraries very cleanly.

I grabbed the source and removed the package bounds and added FlexibleContexts to Control/Arrow/Needle/Parse.hs and everything worked great with stack, but I'm not sure what the best way to contribute this back is... Obviously just removing the package bounds isn't an option, but what would be the right way to approach this?

Anyway, thanks to Needle the diagrams compile just fine :)

I'm happy to do the work to update things in a pull request if you give me a tip about what direction you'd like me to take.