Stream instead of loading all into memory

Now, when you press a note, it won't have to load the entire sample into
memory before playing the note. This means that now you can play many
more notes without it glitching. Frequently, the entire note sample
isn't played, so before there was a lot of wasted processing time
converting the sample into float and doing sample rate conversions if
needed.

Also, perform sample rate conversion on the final rendered-out version
of all the combined notes for a period. This drastically decreases
processing time.

Note: currently having more than one instance causes glitching