Changed update to use prepared statements

Arel changes required for the binding can be seen here:
https://github.com/rails/arel/commit/b4fd431b973e7fc50d3cbf0432b3d8272ac65f0e
https://github.com/rails/arel/commit/9c514f39bd040c45ffa7df43bab24c2a0c88c6e3