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.


Since we're killing 1.8, let's kill this line too and the rubinius one as well.  I'm thinking the list should be

```yaml
rvm:
- "1.9.3"
- "2.0"
- "2.1"
- jruby-19mode
```

You can try also adding an entry for rbx, but we can live without that.