Build symbol->frequency with a function
Rename globas consts in ALLCAPS, add doctests to conversion functions
Encapsulate trial body in a function, don't execute main loop on import
Add missing import
Add additional chirp examples
Switch to more trustworthy exemplar chirp

New exemplar is directly from the chirp.io API, rather than decoded by
eye from an FFT waterfall.
Disable unlikely guesses
Correct tuple packing
Octave/Matlab implementation of reed solomon parameter search
Prototype of continuous phase modulation for chirp playback

chirp.py uses a naive modulation that resets the phase of the sine wave
at each symbol transition. This produces audible clicks in the chirp. By
calculating the phase shift for each same we avoid step changes in the
waveform and get nicer sound.