Very rough and ready demo added
Bunch of changes

Added custom class option
Added data-imagefill-align option, which is overridden by the more
specific halign or valign options
Used image height as the wrapper min height if no wrapper minheight
provided
Add align options for percentages, e.g., align=”23/71”
Optimised code for when width and height attributes are added to the
image. If none provided falls back to wait until the image has loaded
before doing anything.
Added alternate preset name for second third and second golden
Updated docs