* Use SocketRocket pluggable policies
Pluggable policies are currently only in our fork, but pending upstream
PR: https://github.com/facebook/SocketRocket/pull/429
Also:
* rebased SocketRocket against latest upstream to incorporate bug fixes.
* adapt to new upstream API for error handling (vs previous exception throwing)
* renamed AFSecurityOWSPolicy -> OWSHTTPSecurityPolicy to differentiate
it from OSWWebSocketSecurityPolicy
* Follow conventional singleton pattern with onceToken
* bump xcode version to play nice with SWIFT_NAME in SocketRocket
// FREEBIE
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