Support colors in binary STLs

Binary STLs can contain face colors (http://en.wikipedia.org/wiki/STL_(file_format)#Color_in_binary_STL), and the changes support "Magics" color format. 
To demonstrate the changes a new binary STL with colors added, and webgl_loader_stl.html modified to show the changes and usage.

This is how STL looked before:
![before](https://cloud.githubusercontent.com/assets/210621/3638704/b28aa162-105a-11e4-9ac0-8bcc213e847d.jpg)

This is how it looks with extracted colors:
![after](https://cloud.githubusercontent.com/assets/210621/3638708/c662384e-105a-11e4-8af1-c2fbe784faf8.jpg)

The STL file was created by me, so no license is required.