Improve presentation mode (beta)

lib/middlewares.js

@@ -43,7 +43,9 @@ exports.swigFilters = function(app, swig) {
 
     swig.setFilter('presentation', function(string) {
       // 手抜き
-      return string.replace(/[\n]+#/g, '\n\n\n#');
+      return string
+        .replace(/[\n]+#/g, '\n\n\n#')
+        .replace(/\s(https?.+(jpe?g|png|gif))\s/, '\n\n\n![]($1)\n\n\n');
     });
 
     swig.setFilter('picture', function(user) {