Update genres-tree.yaml

Scraped https://en.wikipedia.org/wiki/List_of_popular_music_genres for the first time since @KraYmer did back in (apparently) October 2011. This should be much more useful now to those who have genre canonicalization enabled. Script is in public repo of mine :)
Alphabetize! Thanks @KraYmer
Update genres-tree.yaml
Change expected result for compatibility with updated genres-tree.yaml
Merge remote-tracking branch 'origin/patch-2' into patch-1
Correct busted encoding hopefully
Add support for re-importing added dates.

When re-importing, `item.added` and `album.added` will be preserved if
their path match what they are replacing.
Remove unused function
Check conversion against custom format
Make tests conform to PEP8
convert: Pipepline stage yields result
Merge pull request #924 from nrgetik/patch-1

Update genres-tree.yaml using scraping script <https://github.com/nrgetik/genre-cannon>.
Model.load() should remove flexible fields
Remove BitBucket references
Skip zero-track matches (fix #942)
--version (fix #939)
mediafile: Zero-padded date format

Tag files with '2000-08-01' instead of '2000-8-1'
config: Add suport for 'key in config' syntax

We can use this instead of the cumbersome `config[key].exists()`.
genres.txt: rm fake genres

see issue #943; deleted all suggestions except 'early music' which some people may want/find meaningful
lastbeats: explain that the whitelist has been modified

current description sounds like the whitelist is regularly synced and should not be/has not been edited