fix object number collision on load
new values are 0 by default
don't recompute oscillator frequency if no change

benchmark          old ns/op     new ns/op     delta
BenchmarkSin       9697          6291          -35.12%
BenchmarkFMSin     19192         16171         -15.74%
add fm2 example
update fm2 patch
minor fm2 tweak
add Rand module