PubSub Integration + Speech Improvements

Closes #68

- Imports firebase SDK
- Adds dylib dependencies for Firebase
- Imports Firebase.h into pubsub class
- Adds basic subscribe, publish and unsubscribe
- Adds facebook iOS SDK to appease Parse linker errors
- Re-enables mic listening
- Moves speech recognition logic into VBSpeechKit
- Improves speech reocognition retry speed
  + Shorter speech end detection
  + SpeechKit teardown to force close socket
  + Instant retry after detection
- Receives messages over the Firebase channel