* USB device detection (insertion/ejection) is working.
* Need to remove dependencies on USB serial library.
* Opt for manual control transfer messages to the USB device for device
  communication.
* Basic USB serial communication functionality is working.
* Currently using a sample activity (SerialConsoleActivity) to mask other functionality.
* Need to create a new thread for each user-defined sensor callback object.
* Some code clean-up and commenting necessary.
* Public facing Sensors API is pretty much finalized at this point.
* Need to write actual code for translating values as well as error correction and message format specification.
* Sensor callbacks now functional.  Each sensor callback runs in its own thread.
* The USB sensor task runs in its own thread as well.
* Some more refactoring remains to be done.
* Need to finalize API and remove helper code.
* The USB to Arduino message format and raw value conversion algorithm remains to be done.
* Added some test code to send/receive serial messages from Arduino and Android device
* Milestone for serial communication functionality.
   - Basic support for both ACM and FTDI-type USB devices.
* Need to abstract away ACM and FTDI capabilities better into classes.
* Need to add user-space way to set identifiers for Pulse32 packets.
Final USB serial driver implementation w/ example.
Prepping for merge into master