Update fixes

[khaledkbadr]

Remove deprecated code and fix some clippy warnings

[dwrensha]

Thanks for looking at these things! I think a lot of them would require us to bump our minimum supported rustc version from 1.15 to something newer. I've been planning to tie such a bump to a 0.9 release, which I hope will also update everything to Rust 2018 and use the new stdlib Future trait.

Maybe we should start a branch that you could submit such changes to?

[khaledkbadr]

That would be a great idea if you want to keep 0.8 tied with rustc 1.15

[dwrensha]

I've decided that it would be good to go ahead with a 0.9 release (to be shipped sooner rather than later) that increases our minimum required rustc version and handles some long-planned API changes, without waiting on the Rust 2018 stuff.

I've pulled in your capnp upgrade: https://github.com/capnproto/capnproto-rust/commit/aa28b976949ebc60eac3662b8c2c5f1ed217083f

I've upped the rustc version to 1.26. Is that new enough for the some of the other stuff you want to do here?

[khaledkbadr]

yup, that'd be enough until Rust 2018 is fully complete I think. I was planning to contribute but I wanted first to clear the deprecated stuff and fix the clippy warnings in order to use it as a style guide afterward.