migration script to create backend users referenced in the db

[ztsai]

• fetch all unique (userId and appId) pairs from articles, replyrequests, articlereplyfeedbacks, etc... and create users if it's not a frontend user.

• update userId, appUserId for entities mentioned above

• fetch all unique doc ids from analytics and update userId, appId from the doc

• update fetchStatsFromGA script

• since it's an one off script, integration tests should be sufficient

  • fixtures are created by sampling a snapshot of current db (gist)

closes cofacts/rumors-db#49

[coveralls]

Coverage increased (+0.9%) to 88.156% when pulling 865dc58dabafa214d838e7c46bea9f390e45e50b on createUsers into 77f009788e5f011eb1a8acf7a56d5d1ebc5a6208 on master.