Add support for Map nodes

[bnoon]

I use Map() in my state for ordered lists and would like to inspect them.

[danielkcz]

I think that this should be sorted out in a more generic way, since there is a lack of support for ImmutableJS too (see #51). The Map from ES6 has method toJSON same as the ImmutableJS objects. If we use duck typing for such method, we don't need additional node type in my opinion.

Edit: I am sorry, there is actually just toJS method on Immutable objects. So it would require double check, but it still feels much easier than copy&pasting and changing node.

[bnoon]

I agree that the copy/paste was a quick hack and the common functionality should be pulled out.

However, Map is a built-in object and sufficiently different from Object or Array to be special cased.

[danielkcz]

Yeah, I guess that Map is different, but it's pretty much same as Map from Immutable. There is problem that you can have basically anything in your key, so it cannot be displayed easily in a tree view. Map can be more likely seen as a list of entries with keys and values.

[gaearon]

Can we somehow use iterators + entries() method to have a generic way to enumerate stuff?

[danielkcz]

@gaearon Yeah, I think that might be a good way. The result is in both cases identical (https://jsbin.com/pirura/edit?js,console). And actually entries() is default iterator. It might be enough to check if there is an iterator present obj[Symbol.iterator].

[bnoon]

I am closing this in favor of #79. Thanks @FredyC!

[gaearon]

Should be fixed in 1.1.0, please verify.