Add "atleast = 1" arg to get_show_and_episodes().

In my use of get_show_and_episodes() I only need newer episodes to be
returned, so I added an arg to get_show_and_episodes() that allows an
episode ID to be specified (it defaults to 1 if omitted, for backward-
compatibility).  Specifying this value will stop the routine from
returning any episode objects with an ID lower than the atleast request
(avoiding a bunch of episode instantiations for older episodes).