Add feature for hyper/ssl

[jethrogb]

This is mimicking the setup Iron has. Unfortunately cargo unifies features between dependencies and dev-dependencies (rust-lang/cargo#1796 and rust-lang/cargo#2596). This means that currently, when using iron-test, it's not possible to use hyper without the ssl feature. This PR fixes that.

[jethrogb]

I don't think travis failure is due to this PR.

[shssoichiro]

Is there any reason this PR can't be merged? I need this PR (or the one below it that is nearly identical) merged in so that iron-test won't pull in hyper's cookie dependency (which pulls in openssl ^0.7, which causes version conflicts with reqwest which uses openssl ^0.9). hyper's default features pull this in, but I don't believe iron-test needs it.

I'm dealing with it by putting iron-test in my dev-dependencies, but my CI builds are failing as a result (OS X ignores the openssl version conflict and builds, but Linux fails to compile).

Edit: My Linux deployments are failing as well, the build fails even if iron-test is in dev-dependencies, even if not running tests.

[reem]

I believe this is stale, but please feel free to re-open/fix conflicts if that's wrong!