Strandbeest

This is a slight remix of @nraynaud's Strandbeest Robot. This one differs primarily in that it was designed to be a semi-autonomous using basic obstacle avoidance running an Arduino Mega and various sensors.

Differences from the original:
1. The connector is 20% wider in order to make room for the updated battery holder.
2. The battery holder was redesigned from scratch in Wings 3D in order to allow mounting of an Arduino Mega to the underside and a custom proto board holding the sensors to the top. It was also redesigned to house 4 x 603450 batteries (2 pairs in series to provide 7.4v). A dovetail connection was added to the front in order to mount an IR sensor as it was too wide to pass through the connector opening. Also pre-cut a hole in the front to mount a 9g servo. The sonar holder screws into it for 180 deg distance detection.
3. IR mount for a Sharp GP2Y0A02YK0F (sparkfun.com).
4. Sonar holder for a HC-SR04 (generic).
5. 2 holes in the rear for dpdt switches. 1 swi