NIO Buffer improvements

Turns out Java really does used signed bytes (the heathens), so the
Arpk.nio() method will now attempt to accurately guess the correct data
type of your array (Ruby or Java) for wrapping.

This is for the best, as JOGL's glBufferData() implementation will
accept all NIO Buffer types, so there was really no need to try to
reduce all incoming data to byte buffers in the first place.