fixing issue #348 - instead of returning a server error 500 on article loading which isnt found we'll throw a 404 with json message

app/controllers/articles.server.controller.js

@@ -89,7 +89,11 @@ exports.list = function(req, res) {
  */
 exports.articleByID = function(req, res, next, id) {
 	Article.findById(id).populate('user', 'displayName').exec(function(err, article) {
-		if (err) return next(err);
+		if (err) {
+			return res.status(404).send({
+  				message: 'Article not found'
+  			}); 
+		}
 		if (!article) return next(new Error('Failed to load article ' + id));
 		req.article = article;
 		next();