Completed singleton pattern for BluetoothChatService
Added Constants class for storing the final constants also implemented Singleton pattern for the handler
Complete BluetoothChat on different screen orientations

Finished implementing Singleton to BluetoothChatService and
BluetoothHandler also added sending functionality to "enter" key
Merge pull request #1 from MiichaelD/BluetoothChatService-Singleton

Bluetooth chat service working even on orientation changed