1.0 API

[tsloughter]

Opening this for anyone with particular changes they'd like, whether it is improvements or bug fixes, to please let it be known in this issue so I can take them into account.

I'd like to get to a 1.0 release. Right now I try to stay away from changes that aren't backwards compatible because there is no major version to bump. Of course it is expected that before a 1.0 that anything goes, but it isn't fun for users if every release breaks their usage.

There are a number of exposed functions I think can be removed and stream callbacks need to be improved. This is going to have to be done carefully to not mark a 1.0 and then find out their are bugs requiring API changes right away :).

I'd also like to dig into h2_connection stream handling and verify there aren't some unnecessary bottlenecks (as in, operations that don't have to be done within the single process). For example, maybe if streams are in a protected ETS table instead of a list it'll be possible to move some operations out of the single process.

A good bit has changed in OTP since this library was written as well, so more moving to use of maps where possible and using uri_string to have a better client request interface.