fix migrations and tweak things to remove hard dependency on mysql
fix more deprecated methods from Sequel
Merge remote-tracking branch 'mrbrdo/fix_migrations'
Fix migrations MySQL compatibility
Bugfix for the number of unreviewed commits

num_unreviewed_commits was doing something different than indicated - counting the number of commits without comments. 

Now it simply counts the number of commits that have a null approved_by_user_id.
Merge branch 'fix-number-of-unreviewed-commits'