Pass through key event when calling keyboardCondition() to allow conditional function to filter on key codes

Added programatic support for custom key bindings with optional descriptions to be added to the help screen

Add an option to auto-slide right only

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

stops parallax failing if only the single horizontal slide and multiple vertical

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

Update the theme README.md

Fix text being cut off in Chrome when printing.

Fixed #1379 - config keyboard now disables 's' key

Fixes #1225

always enable highlight.js to fix markdown-only usage

Add more support for external markdown.