Merge pull request #57 from RolandReyer/Rolands

Info icon and hotkey to toggle the footer

fix #52 #55

prevent zoom controls when zoom is disabled

fix fullscreen state when open gallery

fix fullscreen detection

fix missing scrollbars (Firefox)

update custom animation (demo page)

force apply custom classes

add option for custom classnames

update readme

cleanup and refactoring

improve preloading and cancelation

cancel preloading of next image

improve termination of background loadings