read me and tests fixed

Author: keithbooher

README.md

@@ -78,8 +78,7 @@ Lazyload::Rails.configure do |config|
   # This can be easily customized:
   config.placeholder = "/public/img/grey.gif"
 
-  # By default lazy_css_class is nil. 
-  # If configured a css class will be added to all image_tag's with lazy: true for easy styling
+  # All lazyload images can have an additional classes added to them for easy DOM querying
   config.lazy_css_class = "lazy_images"
 
   # image_tag can return lazyload-friendly images by default,