Changelog for map-exts- Remove functions which are superseded by upstream

containers has added take, drop, restrictKeys and withoutKeys which are equivalent to take, drop, keepKeys and dropKeys from the map-exts API, respectively. takeLeft/Right and dropLeft/Right have been exposed.

containers:drop/take correspond to dropLeft and takeLeft respectively.

map-exts is now compatible with lts-10.3 Add version bound for upstream containers Improve documentation, examples