Pull and Push thresholds, auto-pull and auto-push

[kamocat]

There's currently no configuration for pull or push thresholds, or to enable auto-pull and auto-push. This means instructions like jump !osre will count to 32 rather than my desired word size.

These options could be added to the emulate function.

At some point it might make sense to refactor into a class, with the configuration done during initialization and a step method which accepted inputs and returned outputs. This would break existing code and require a major version, but it would create explicit state storage and allow multiple state machines to cooperate.

[NathanY3G]

Thanks for bring this deficiency to my attention @kamocat. I've added it to my to-do list.