Auto-sliding will now use the method specified in the config if it is
a function or default to navigateNext.

When the autoSlideRight config option is active, the auto-sliding
will always navigate to the right and never down even if slides are
present there. This allows hidden "bonus slides" in presentations
which can be displayed as needed but won't show up automatically.

check for 0 division, stops parallax failing if only the single horizontal slide and multiple vertical

Removed toLowerCase call

This will maybe solve the "InvalidStateError: An attempt was made to use an object that is not, or is no longer, usable" error in firefox.