Add support for iterative inference

[gtfierro]

Adds a new flag, -maxiterations which takes an integer argument. This defaults to '1' (which was the existing behavior). The new Infer implementation performs the inference until either (a) the required nubmer of iterations is hit, or (b) there are no new inferences produced. Resolves #162

@HolgerKnublauch I didn't see any CONTRIBUTING document so let me know if there's anything you'd like me to add here. Is there a particular test file I should be adding some calls to? Linters/checkers you want me to run?

Thanks in advance!

[gtfierro]

I've applied the fixes you mentioned. Thanks for the review!

EDIT: I've also updated the README to mention the new argument

[gtfierro]

Thanks!