Update sequelize for version 3.0

[mlms13]

There are some security fixes... mostly things that don't let you use features in ways that could lead to security holes, not actually fixing security holes in sequelize itself. Would be good to update though, as the API for some methods has changed slightly.

[mlms13]

Not sure what changes we need to look for specifically... we've been using Sequelize 3+ for awhile without problems.