Nick/host prevention now actually verbose-only

f3e6117 changed it for rate limiting, not nick/host blocking
[dice] Add example tests.
[dice] Rewrite dice rolling.

-Do arithmetic locally, instead of using google.
-Don't call random unnecessarily.
-Add compressed view of the dice, for when there are too many to list.
-Limit number of dice to 1000. Fixes #309.
[test_tools] Make the assertion message for regexps more readable.
[tools] Add ExpressionEvaluator class and eval_equation function.
[dice] Add back arithmetic expression functionality.

-Also allows for using many dice expressions in one command, just like before.
[module] Fix decorators in nickname_commands docstring