Merge pull request #136 from Valve/master

Keep up with rust
Propagate OpenSsl errors.

We lift OpenSsl errors to IoErrors, conditionally losing some information.

Without a better error abstraction, this is the best we can do without
specializing Connecter to OpenSsl.

Fixes #137
Merge pull request #138 from reem/ssl-fix

Propagate OpenSsl errors.
Add serve_once method to Server