A slider to compare two overlaid images. Uses Juxtapose JS.
_startingPosition (string): The position from the left to have the slider (default: 50%)
_leftImage, _rightImage (object): Options for each of the images
src (string): The source for the image
label (string): A label that accompanies each image, appears in the top left/right corner.
credit (string): Attribution text that appears below both images.
Version number: 1.0.0 
Framework versions: 2.0 and greater
Author / maintainer: Simon Date contributors
Accessibility support: No
RTL support: No
Cross-platform coverage: Chrome, Firefox (ESR + latest version), Edge 12, IE 11, IE10, IE Mobile 11, Safari for iPhone (iOS 8+9), Safari for iPad (iOS 8+9), Safari 8