fix more kinds of whitespace in URIs, including tabs
add msgpack-JSON converters, remove old JSON builders
Update tests for msgpack and new DB format
remove a language code that was probably mistaken
when normalizing usernames in ConceptNet 4 sources, don't lowercase them
regenerate ConceptNet 4 sample output to include nadya.jp
allow titledb=None, to avoid creating an empty file

These tests were previously setting titledb to 'abc', and the result was
to create an empty SQLite database by that name in the current
directory. Now, if titledb=None, it creates the fake titledb in memory
instead.