* Updated some outdated repo urls in json file
* Removed default CSS height for images
* Repurposed 'thumbnailDimensions' to set image max-width/max-height CSS whenever thumbnails are not generated -- when 'thumbnails' = false, or image is ignored by 'thumbnailExcludeFilter'
** Default is unchanged: { height:100, width:null }
** This gives implementors much more control over thumbnail size, without the need to set CSS
* Fixes #30
* A couple of CSS tweaks