Emitter fixes (WIP)

Hello again :) Opening the PR early as you suggested.

I enabled 1.9 style hashes in `Emitter::Literal::HashPair` & `Emitter::Literal::Primitive::Inspect::Symbol` (the class I've extracted from `Emitter::Literal::Primitive::Inspect` to add the new logic). I'm not really sure it's the best way to implement this feature so I'm waiting for your approval.

Next I'm going to work on empty lines between sibling method definitions.