Update dependencies
The $property_map property should be a static property
Re-format the Collection class definition to be better readable
Separate data parsing upon instanatiation into separate method
Clarify docs for Collection::add() method
Implement Collection::push()
Implement Collection::pop()
Remove Collection::keys() - the method mapper can take care of this functionality for free
Add new read-only properties: "keys" and "values"
Document all read-only properties of Collection