Mobot

- Add Exception for AssetNotAvailable
- Split the package into mobot and mobot_utils
- refactor according to PEP8 and PEP257
- Bug Fixes

Updates:
1. Moved from robot velocity interface (i.e. v, w) to robot wheel velocity interface (i.e. wr, wl) for chassis.
2. Teleop using pyqt based dashboard with the following features:
1. joystick to control chassis
2. image window to view camera stream
3. check box for flashlight
3. Bug fixes in chassis firmware
4. removed mobot_awake face from android app

Features
* Android app capable of:
* Streaming camera, accelerometer, magnetometer & gyroscope data.
* Can on/off flashlight
* cmdvel interface to the chassis
* Initial mobot python package
* Initial chassis
* ball_follower demo