v1.7.0

• The window on furbo.get_events is now optional. Leave start and
  end out and you get the most recent events with no time filter at all;
  give one end alone for everything since, or until, a moment.
• Why this matters beyond convenience: the action still returns nothing on at
  least one account, and a window the cloud does not filter the way this
  integration expects is indistinguishable from a week with nothing in it.
  Both come back as an empty list. Asking with no window at all is the one
  call that separates them, and until now the action would not let you make
  it. Refs #6.