Support for client-side manual trust evaluation (cert pinning) via delegate callbacks.
Merge branch 'certpinning' of https://github.com/appscape/CocoaAsyncSocket into appscape-certpinning
Removing SECURE_TRANSPORT macros. iOS 5+ is now required (and has been for awhile now)
Improvements for manual trust evaluation. Addresses issue #161. Changed delegate method "socketShouldManuallyEvaluateTrust:" to be an option passed into startTLS. Also fixed the delegate invocation to dispatch asynchronously.