Added nimrod version

https://github.com/Araq/Nimrod
Updated nimrod version with new graphic
Removed comment
Add command line options
Read art from file
Use options in thread block
Save rendered image to output file
Only retrace if Lambertian factor >= 0
Constrain ray direction to an aspect ratio
Clamp pixel channel colors to 255
Cache common vectors
Update object offsets
Update rubyrays readme

rubyrays no longer writes to stdout by default.
C++: Remove unnecessarily instance of Objects
C++: Implement external ART file reader
Fix typo in megapixels description
C++: Implement Go style command line interface

 * There is no usage option.
 * Result file is not implemented yet.
C++: Remove in-place member initializer to support GCC 4.6
Update readme to reflect the new output filename
C++: Implement result file (JSON)