Initial implementation of interceptors.

I'm anticipating implementing interceptors at two independent parts
of the API. The first is high-level interceptors, that intercept
before the socket connection has been established.

The second set of interceptors will only execute for requests that
require a socket connection. Those are forthcoming.
Merge pull request #1193 from square/jwilson_1207_interceptors

Initial implementation of interceptors.
Change COMPATIBLE_TLS to be TLSv1.0 and not SSLv3

Based on a discussion with Jesse Wilson during
https://github.com/square/okhttp/pull/1189.
Merge pull request #1196 from nfuller/SwitchOffSslv3

Change COMPATIBLE_TLS to be TLSv1.0 and not SSLv3
bind specifically to a loopback interface and add dependency on animal sniffer 1.13