add vary header, first draft
Merge pull request #193 from wenderen/vary-header

add vary header, first draft
feat(client): add a new Client struct with super powers

- Includes ergonomic traits like IntoUrl and IntoBody, allowing easy
usage.
- Client can have a RedirectPolicy.
- Client can have a SslVerifier.

Updated benchmarks for client. (Disabled rust-http client bench since it
hangs.)
Merge pull request #182 from hyperium/client

feat(client): add a new Client struct with super powers
proc() -> move ||
Change implementation of AnyRefExt for references to NetworkStream to require 'static lifetime
Merge pull request #198 from Ogeon/master

Rust update: Remove proc and implementation of AnyRefExt for static NetworkStream