Finalize uniquification by actually using the value. Only to be merged after all rows have data_sha256 values.
Merge branch 'master' into uniquify-2

Conflicts:
	acousticbrainz/server.py
Add upgrading of index to UNIQUE and deletion of duplicate values to upgrade_data_sha256.py
Merge pull request #2 from metabrainz/uniquify-2

Uniquify, part 2