pages: get last page by default with RSM: When `max_items` is not used, Pubsub (and thus RSM) is actually returning results in chronological order. As most of time we want latest items first, `getPubsubExtra` now set `before` to get last page by default (the one with most recent items).

import os.path

version_file = os.path.join(os.path.dirname(__file__), "VERSION")
try:
    with open(version_file) as f:
        __version__ = f.read().strip()
except NotImplementedError:
    # pyjamas workaround
    __version__ = "0.7.0D"