- add configuration option for density (0.1 - 0.9)
- clear the screan after ctrl+c (seems like termion is supposed to handle this, possible we are not awaiting the completion of a thread)
- traces should update at different rates
- stagger updating of characters (reduce "pulsing")
- permit overwrites (multiple traces in the same column)
- add configuration option for overwrite behavior (deletes the trace it catches vs being followed by it)
- handle terminal resizing (see termion's `terminal_size()` function)
  - when window size decreasing, delete out-of-bounds traces
  - when window size increasing, start sliding again / add new traces
- add configuration option for trace "gravity" (tendency to cluster together rather than simple random placement)
- option to --debug which will reserve a few lines at the top of the screen dedicated to debug info
  - update delay
  - updates / sec (frequency in Hz)
  - glyphs / sec
  - glyphs / update
  - traces / update
  - min/max glyph delay (actual, not the configured min/max)