Backbone doesn't respond to changes in ES5 Maps/Sets, even new ones

[martingraham]

Backbone compares old and new .set values using the Underscore libraries isEqual method.

This at the moment doesn't work for Maps/Sets, it will return equals is true for any two Maps or any two Sets

It's getting worked on jashkenas/underscore#2451

but will need some sort of hacky fix in the meantime (Backbone has some sort of force change method).

That took most of the day :-)

[martingraham]

Fixed by forcing Backbone change event, will do it normally once underscore updates to fix this