Adds options object, implements option implicitOptionalChaining, tests...

[mshick]

I needed some functionality to evaluate expressions against an unknown context of query results. As such I have no guarantee that results.foo and results.foo.bar exist when I try to access them to determine whether my step will run. Catching thrown errors is not sufficient either, as an expression might evaluate against many results, which may or may-not exist, e.g., results.foo.bar == true || results.baz.bar == true.

This PR adds an optional behavior to use an optional-chain when evaluating the object member expressions when the implicitOptionalChaining option is set to true. It also adds in support for options, and restructures the functions to do that in a more convenient way (similar to this PR #42).

I also added some tests that validate the new behavior and ensure the old throw behavior still works.

[donmccurdy]

Hi! I'm open to adding this option, but the restructuring makes this PR too long for me to review (similar to #42). Do you mind omitting the reformatting, or moving that to a separate PR with no other effects?