A simple and fast two-way async channel.
Benchmarks for v0.2.0:
function/call [1.5749 ns 1.5818 ns 1.5887 ns]
extern/call [1.5249 ns 1.5355 ns 1.5452 ns]
ffi/call [2.9104 ns 3.3309 ns 3.8884 ns]
whisk/call [213.22 ns 214.15 ns 215.03 ns]
flume/call [512.15 ns 537.62 ns 572.21 ns]
whisk/threads [10.455 us 12.039 us 14.052 us]
flume/threads [13.157 us 15.460 us 18.298 us]