Merge pull request #2307 from sinzianag/swift_protobuf

Docs: Link to Apple's Swift plugin and runtime for protobufs

docs/third_party.md

@@ -83,6 +83,7 @@ These are projects we know about implementing Protocol Buffers for other program
 * Scala: https://github.com/SandroGrzicic/ScalaBuff
 * Scala: http://trueaccord.github.io/ScalaPB/
 * Swift: https://github.com/alexeyxo/protobuf-swift
+* Swift: https://github.com/apple/swift-protobuf/
 * Vala: https://launchpad.net/protobuf-vala
 * Visual Basic: http://code.google.com/p/protobuf-net/