Fixes #31 - 16bit sample loading.
Fixes #31 - 16bit sample loading.

 * The code for loading and converting 16 bit sample data wasn't
working. According to the FT2 docs, the data is just 16 bit signed
deltas, so I've changed the code to match the 8 bit conversion code and
follow the simple accumulation strategy and it seems to work a lot
better.

pgregory/wetracker,pgregory/wetracker