Scroll vertically when reaching the last slide when swiping horizontally

### Description
First off: great plugin. Making a pretty cool animated infographic using it.

The following description is included in the codePen as well:

## Issue
Using the scrollHorizontally extension and setting `continuousScrolling` to `false` has mixed results depending on mobile/desktop and gesture/scroll direction.

### Results on mobile (iOS Safari and Chrome)
Left and right gestures - **Do not work properly**. Slides continuously scroll.

- Swiping right on the first slide returns to the final slide instead of returning to the previous section.
- Swiping left on the final slide returns to the first slide instead of advancing to the next section.

Up and down gestures - **Works properly**. Slides do not continuously scroll.

- Swiping down on the first slide returns you to the previous section.
- Swiping up on the final slide advances you to the next section.

### Results on desktop (macOS Mojave Safari and Chrome)
Mouse wheel up and down - **Works properly**. Slides do not continuously scroll.

- Mouse wheel up on the first slide returns you to the previous section.
- Mouse wheel down on the final slide advances you to the next section.

## Expected behaviour
Left and right swipe gestures on mobile do not continuously scroll when continuousScrolling is set to false and that they advance you to the previous/next sections.

### Steps to reproduce it
1. Open the fiddle on desktop - observe results when using the mouse wheel to move between slides. Setting continuousScrolling to false works properly.
2. Open the fiddle on mobile - observe results when swiping left and right and up and down. Swiping left and right does not work and continuously scrolls, yet swiping up and down works properly and does not.

### Versions
Desktop: macOS Mojave Safari and Chrome
Mobile: iOS Safari and Chrome