Fix for UnicodeEncodeError in notification function.

Add encode method to message string in utilities notification function.

Encountered this error when I manually marked an episode 'Jo - S01E05 - Place Vendôme' as watched in XBMC, the **ô** triggered the error.  This is fixed in the notification helper function, by encoding the message to utf-8 in the string formatting.

Since this is a helper used throughout the plugin, may solve other encode errors not yet encountered.

Needs to be tested to make sure it doesn't have any side effects, but I don't believe there are any.