• Improve the mechanical design

I've made a few more improvements since improvements.

• Added optoswitches for zeroing axes,
  • Tabs on arm1 and arm2 to pass through the optos,
  • An arm to hold the optos.
• Rotated the pin hole that holds arm1 onto shaft1,
• Rotated the angle of the split that holds the two halves of arm1 together.

• Assemble everything