tests: Use audio instancee, not module
docs: Formatting. Remove promises of sound quality
Update changelog
docs: library.{find_exact,search}() returns all tracks if no query
docs: Add SearchResult to models diagram
mpris: Add artUrl support
mpris: Add discNumber support
core: Warn if track isn't playable
docs: Add info about mailing list
models: Comment Album.images not preserving order
Use thread traceback logger from Pykka 1.1
Turn thread traceback logger on by default

It no longer requires an additional thread to work and it is very useful to
have this enabled when you hit an issue that is hard to reproduce.
docs: Recommend pkill instead of ps+kill
fix lookup of filenames containing non-ascii characters
docs: Add initial extension development docs
docs: Move extensiondev file
docs: Add intro to extdev
docs: More extdev notes
docs: Initial example files for new extensions
docs: Fix list formatting