Incompatible with Object.create(null)

[tad-lispy]

Hello. Thanks for seamless. It's a very nice piece of software.

I was surprised however that I cannot create immutable object from an object without prototype (e.g. acquired with Object.create(null):

Immutable(Object.create(null));
// TypeError: target.hasOwnProperty is not a function

It is also impossible to merge such an object into immutable:

var o1 = Immutable({a: 1});
var o2 = Object.create(null);
o2.b = 2;
o1.merge(o2);
// TypeError: other.hasOwnProperty is not a function

Obviously it depends on hasOwnProperty method of the original object, which is usually available in a prototype chain.

Can we use global Object methods instead, like Object.getOwnPropertyDescriptor? I'll be happy to provide PR, but would like to discuss it first.

[rtfeldman]

I'm surprised by this too! Assuming it wouldn't have noticeable performance costs, I'd be happy to accept a PR that fixed this.