replace equality check with bulletproof solution

[cpeddecord]

This issue has hamstrung certain aspects of local development vis a vis:

• npm link would cause multiple instances of Immutable to be referenced
• working within a mono-repo tooled by Lerna causes multiple instances of Immutable to be referenced

Could this be solved using something like Immutable.Map.isMap() vs. comparing constructors?

[cpeddecord]

#14

passes tests on your end, passes tests on my end.