0.2.4

Changes the behaviour of assoc-un: if key is not present, returns the original map

This is more logical. Assoccing to a nil value or an empty map should be equivalent to associng to a key which is not present in the map => the result is the original map (if we have a namespaced map, which does not contain the key used in assoc, we do not want that unnamespaced key to be added in the map).