[BUGFIX] Eliminate real-time allocations in WaveNet

[sdatkinson]

• Non-gating WaveNet should be real-time safe (benchmodel with example WaveNet runs clean).
• Some tests would be great though.

Sort-of breaking changes (causing me to bump to 0.3.0):

• Reset() calls prewarm(). (This is now ok because it calls SetMaxBufferSize() first, which can handle allocation of model arrays.)
• mMaxBufferSize defaults to 0 instead of 512 on construction. This is nice and conservative but might break code that was expecting teh mdoel to come "ready to go" out of get_dsp() (However, Reset() should be called before using the model!)

Resolves #49

[sdatkinson]

Ugh, I need to get #140 sorted. I'll get that figured out before I release 0.3.0.