Fix for capitalized URL schemes in autolinks.
Fix for capitalized URL schemes in autolinks.

ashur/php-markdown,drosenstark/php-markdown,MWDelaney/bootstrap-3-shortcodes,mariokonrad/php-markdown,jockchou/php-markdown,MWDelaney/bootstrap-3-shortcodes,alganet/ElephantMarkdown,robbieaverill/php-markdown,filipstefansson/bootstrap-3-shortcodes,nazar-pc/php-markdown-next,filipstefansson/bootstrap-3-shortcodes,MWDelaney/bootstrap-3-shortcodes,n054/php-markdown,c9s/php-markdown,itafroma/php-markdown,TypeFriendly/PHP-Markdown,Kapeli/php-markdown,queirozfcom/php-markdown-with-syntax-highlight