Use 'Protocol' to describe framing.

Drop setTransports/getTransports which was deprecated in favor
of protocols.

Rename setFollowProtocolRedirects to setFollowSslRedirects. I decided
to use SSL rather than TLS for consistency with nearby APIs.
Merge pull request #722 from square/jwilson_0418_even_more_protocol

Use 'Protocol' to describe framing.