The `audiotospectrogram` module is a complete rewrite of the existing spectrogram
code with support for Python 3. This allows us to drop the bundled `freesound`
library and Python 2-only `audioprocessing` and `spectrogram` modules.
Signed-off-by: Ben Sturmfels <ben@sturm.com.au>
Mostly a thorough test and cleanup. The significant change is moving the systemd
config into the deployment docs an the registration/security considerations to
production considerations docs.
For 0.10.0 we're removing specrograms entirely for reliability. This change only
disables spectrograms and updates install docs and Dockerfiles. We still need
to strip out all the spectrogram code and extlib/freesound/.
