Run security audit

[sinahab]

Using this as an ongoing issue to keep track of points for a future security audit.

[sinahab]

• Does this function being internal as opposed to private cause issues? dbe24c5#diff-93850d9c4a6879f5d1697913e31c1501R34

[sinahab]

• Refactor how the runNextVerificationGame is triggered. This currently costs the innocent caller a lot of gas.