Add PEP484 type hints

[wwuck]

Proposal to add PEP484 type hints and related PEP561 packaging information to inflection. Since the lowest support python3 here appears to be 3.5, we can just use typing library directly without using type hint comments.

[wwuck]

Just realised that Pypy doesn't appear to support type hints :(

https://doc.pypy.org/en/latest/faq.html#would-type-annotations-help-pypy-s-performance

Would that be a blocker for this issue?

[jpvanhal]

Hi, thanks for the proposal and the PR! I've been thinking about adding type hints myself as well :)

Just realised that Pypy doesn't appear to support type hints :(

doc.pypy.org/en/latest/faq.html#would-type-annotations-help-pypy-s-performance

Would that be a blocker for this issue?

I was checking the Travis logs for your PR and it looks like the Pypy build is failing to install typed-ast package. See also python/typed_ast#111.

typed-ast is a dependency of mypy. If installation of mypy and thus the static type checking was skipped on Pypy build, I'd assume that would make the whole build green. So I don't see this as a blocker.

[wwuck]

I've skipped mypy on pypy3 tox run, so it should all be fine on the PR now.

[jpvanhal]

Thanks, @wwuck! This is included in v0.5.0.

[henryiii]

It looks like you added type hints (fantastic), but forgot to add the py.typed file to your MANIFEST.in, so downstream projects can't use it. :'(

I'd highly recommend check-manifest to avoid this in the future. Maybe in a pre-commit check or something. docs.