upgrade Rails to 4.1.2
db: reorganize accounts (remove private, rename notification to notification_enabled, add index)
db: optimize users table
web/api: User#count_discovered_by sums up 500 tweets
web: tweets#show: import tweet only if the tweet is not found
web: update policy for unregistered user: unregistered users' best is now available
collector: change account state to revoked when recieved unauthorized