More documentation updates

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Update MANIFEST.in

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Update sphinx configuration
Move sectors_to_seconds to libdiscid

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Add __all__ in libdiscid.compat.discid

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Fix handling of None in read

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Release 0.3.1

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Merge branch 'bugfix-0.3'

Conflicts:
	docs/conf.py
	libdiscid/__init__.py
	setup.py