This includes several improvements to prevent circumventing protection controls:

• Replace the system to prevent overriding methods in classes. The new one is based on .freeze and it also prevents changing class-level state. A big flaw in the previous approach, based on the method_added hook, is that, while it raised an error, it wouldn't prevent the command from executing (it was evaluated after).
• Prevent using instance_variable set on core classes.
• Prevent opening ActiveRecord classes for monkey patching them.
• Prevent modifying config options once a console session has started.
• Prevent load sensitive constants dynamically (Console1984, ActiveRecord).
• Freeze Socket classes and database connection classes to prevent overrides. Also prevent instance-data manipulation for the later.

It also includes a new system for testing tampering cases that should be detected: just place the snippet test/tampering_cases. A test will run for each file and it will fail if it's not detected.

Fix #19