Fix for #74.

[cardboardcode]

Purpose of Pull Request

This pull request introduces edits into the following .dae 3D model files that addresses the issue identified in #74.

The dae files edited are as listed:

1. mycobot_description/urdf/mecharm_pi/base.dae
2. mycobot_description/urdf/mecharm_pi/link1.dae
3. mycobot_description/urdf/mecharm_pi/link2.dae
4. mycobot_description/urdf/mecharm_pi/link3.dae
5. mycobot_description/urdf/mecharm_pi/link4.dae
6. mycobot_description/urdf/mecharm_pi/link5.dae
7. mycobot_description/urdf/mecharm_pi/link6.dae