Add support for Big and Little Endian modifiers

This pull request also fixes encoding issues in existing tests caused by upgrading ruby from 1.8.7 to 1.9.3.
@Fryguy, @chessbyte please review.


> existing rbx-19mode

Yes rbx == rubinius.  You can leave it in, but if it's failing on Travis, then we can take it out.

> jruby run in 2.0/2.1 mode

I don't think so, but I'm not 100% sure.