Comply to interface

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
PEP8 compliance

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Generate proper filename for audio types (fix #99)

Includes unit test for util.generate_filename.

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>