Add support of allow anonymous config option with correspond modifications

lib/response.js

@@ -60,6 +60,7 @@ function showIndex(req, res, next) {
     res.render(config.indexpath, {
         url: config.serverurl,
         useCDN: config.usecdn,
+        allowAnonmyous: config.allowanonmyous,
         facebook: config.facebook,
         twitter: config.twitter,
         github: config.github,
@@ -92,6 +93,7 @@ function responseHackMD(res, note) {
         url: config.serverurl,
         title: title,
         useCDN: config.usecdn,
+        allowAnonmyous: config.allowanonmyous,
         facebook: config.facebook,
         twitter: config.twitter,
         github: config.github,
@@ -106,6 +108,8 @@ function newNote(req, res, next) {
     var owner = null;
     if (req.isAuthenticated()) {
         owner = req.user.id;
+    } else if (!config.allowanonmyous) {
+        return response.errorForbidden(res);
     }
     models.Note.create({
         ownerId: owner