Move somes functions to be after RAVEN_ALERT is applied; fixes #609

This MR fixes #609 (closed), an issue where functions (external_skymaps.plot_overlap_integral and raven.update_coinc_far) that need to know whether the current joint candidate has the RAVEN_ALERT label were being run before the function that applies this (raven.trigger_raven_alert).

This fixes this by placing those two functions within raven.trigger_raven_alert, adding the RAVEN_ALERT to the local superevent dictionary, and then running these two functions.