Fix promise on properties and refactoring - #112

Fixes #97

It's mainly a refactor pr with some bug fixes. The refactor merges the FunctionState and GetState into one class, as both classes had the same logic but spreaded around. I couldn't come up with a name for the new file and class, but I image something like GetApplyPropertyState could work?

Fixes:

• .resolves and .rejects not working on properties
• zero inputs in substitute methods with required return type not being treated as errors

interface Calculator {
  add(a: number, b: number): number;
}

const calculator = Substitute.for<Calculator>();
calculator.add(1, 1).returns(); // Expected at least 1 arguments, but got 0 - this was not being treated as an error before this pr