Aitk.robots

Major changes:

* Fixes for pen and speak at time 0
* Allow int width and height on World.watch()
* Changed robot repr

Major changes:

* Enabled circle-ci integration testing
* Devices only accept valid config keys now
* Bulb drawing enhancements

Major changes:

* made many attributes "private" (renamed with leading underscore)
* removed camera viewport; set defaults
* don't allow extra keywords for world and robot
* updated worlds with direction -> a

Major changes:

* Added Robot.get_velocity(target=False)
* Don't color entire robot when stalled; now just border is white
* Robot.reverse() flips all velocities (vx, va)
* Added Robot.rotate() and Robot.translate(); same as Robot.turn() and Robot.forward()
* Renamed all take_picture() to get_image(), returning a PIL Image
* Renamed all direct to a (in robot and devices)
* You can draw on world with world.canvas.draw_line(), draw_circle(), etc.
* Camera images are less curved than before

Major changes:

* Fixed issues with robot direction
* Adjusted RangeSensors to properly convert direction to world coords

Major changes:

* Fixed Robot direction coords in constructor and JSON in/out
* Added Camera.orthographic (distance is to camera plane) vs. perspective mode (distance is to camera point)