Flexible buffers and oscillators

purescript-wags now uses strings instead of symbols for setting buffered content. This is a breaking change that moves buffers conceptually closer to other generators. For example, in a sine-wave oscillator, a frequency that changes over time determines what one hears. In a buffer, the buffered audio can be thought of in the same way: it can change over time. That said, changing buffers mid-flight leads to glitchy sound, so the change only takes effect once the buffer is off.

The library also uses strings instead of symbols for setting the real and imaginary parts of periodic oscillators (see above).