Made image tag regex smarter, fixes #239

plugins/image_tag.rb

@@ -24,7 +24,7 @@ module Jekyll
     def initialize(tag_name, markup, tokens)
       attributes = ['class', 'src', 'width', 'height', 'title']
 
-      if markup =~ /(?<class>\S.*\s+)?(?<src>(?:https?:\/\/|\/|\S+\/)\S+)(?:\s+(?<width>\d+))?(?:\s+(?<height>\d+))?(?<title>\s+.+)?/i
+      if markup =~ /(?<class>[\S\s]*?)?\s*?(?<src>(?:https?:\/\/|\/|\S+\/)\S+)(?:\s+(?<width>\d+))?(?:\s+(?<height>\d+))?(?<title>\s+.+)?/i
         @img = attributes.reduce({}) { |img, attr| img[attr] = $~[attr].strip if $~[attr]; img }
         if /(?:"|')(?<title>[^"']+)?(?:"|')\s+(?:"|')(?<alt>[^"']+)?(?:"|')/ =~ @img['title']
           @img['title']  = title