Allow use of arbitrary values as state and event tags

[mrnerdhair]

TL;DR: I switched the Object.create(null) objects used to keep track of state and event configs with new Map(), and made sure no assumptions are made regarding what objects get fed in. Strict equality semantics (===) are used when determining which state/event is being referred to in any calls.

There are also some improvements regarding testing in here; I wrote a harness to allow running multiple instances of each unit test, one for each of 8 types of keys.

[mrnerdhair]

(closing/reopening pr to trigger retest)