Merge pull request #337 from jonasman/master

Removed compiler warnings from unused xmpplog variables
Merge pull request #338 from jonasman/master

fixed compiler warnings, removed unused log variables 2
Implemented SASL SCRAM-SHA-1 Authentication

RFC5802 http://tools.ietf.org/html/rfc5802

Support for SHA-1 but would be easy to support other hashing algorithms
in the future. Does not support channel binding.
Merge pull request #341 from ChatSecure/scram-sha1

Implemented SASL SCRAM-SHA-1 Authentication
XMPPMessageArchiving Default Log Level
sharedInstance Storage now use instancetype

Fixes #343
XMPPStream validatesResponses API

Facebook doesn't respond from the correct JID during negotiation so I making the validation of responses optional for now.
Upgrading GCDAsyncSocket to 7.4 branch, commit 5aa4d2145570ec0cd107e508ca0799b2df0dbabe
Fixing / upgrading Xcode projects
Adding support for SSL pinning. Fixes issue #333
Fixing sample projects to use new TLS certificate evaluation callback style.
Added element ID when requesting vCards