add regression tests for feature lists
add a simple disc test, re #18

This tests "read" and calculating an id.
That is not supported on the generic platform, but that shouldn't be a
problem. This test is not in the standard list of tests.
last_track_num is last audio track
complete disc test suite, close #18
check test results are the same after read and put
tests: remove a description from output
add track_length, re #5
add webservice_url, re #5
merge tests for None
more emptyness checks
add freedb_id, re #5
add new API to doc
update CHANGES
set version to 0.4.0
set version to 0.4.0-dev
Merge branch 'master' into isrc_api

Conflicts:
	discid.py
	doc/discid.rst
add tests for mcn api