Set version to 1.3.7, fix flashing main menu animation.
Clean up main menu animations.
Only enable fadein for Episodes the first time a background changes.

Previously the fadein if enabled for episodes would always fade in regardless
if the background image had changed or not.  This only sets the background
image to change if the series title has changed.
Set version to 1.3.7-snapshot
Remove unused variables.
Release v1.3.7