Adds notes about why a frequency around 19kHz was chosen.
Fixes Issue #12, where checking around a frequency that is very close to the edge of the fft would cause an index out of bounds. Also makes checking around around a frequency a little more robust.
Updates options use a chunk size of 256 and a frame_length of 3. This makes things a bit faster and still seemed to work well.
Merge remote-tracking branch 'upstream/master'