BUG: Tuple types are not correctly inferred from literals.

[leebyron]

I've encountered this a bug (or at least, @calebmer told me it's a bug) where tuple types are not correctly inferred, so the only way to correct a flow error is to manually add in the type - which can get verbose.

Here's an example where I'm attempting to deeply "unwrap" polymorphic classes with the type they contain.

This pattern appears in both Immutable.js conversion functions and TestCheck.js generator functions, and I'd love to get them properly typed.

leebyron/testcheck-js#79 tracks this particular bug's limitation on TestCheck.js's types.

Any ideas, @avikchaudhuri or @samwgoldman?