Improved Clip-on Tool Holder (BI 2.5)

Originally inspired by http://www.thingiverse.com/thing:673497, but designed from scratch for my own needs.

This tool holder clips onto one of the lower corner pieces of the BI 2.5

It holds:
- 5 Hex Wrenches (5mm, 4mm, 3mm, 2.5mm, and 2mm)
- Metal scraper
- Tweezers
- Needle nose pliers
- Plastic scraper (http://www.thingiverse.com/thing:596563)
- Generic 20mm circular slot (currently used to hold mini bit driver http://www.thingiverse.com/thing:397940)