guarantee ordering when using leveldb back end

startup might be a little bit slower now
but we shouldn't see "too much recursion" errors
closes #6 (in theory)

storage/lvl.js

@@ -59,13 +59,19 @@ module.exports.create = function(conf,cb){
         getMessages: function(cName, cb){
             /* get all messages relating to a channel */
             getIndex(cName, function(index){
-                for(var i=index;i>=0;i--){
-                    db.get(cName+'=>'+i,function(e,out){
+                var last = index,
+                    i = 0,
+                    next = function () {
+                        db.get(cName+'=>'+i, function (e,out) {
                             if(e) return console.error(e);
                             cb(out);
-                    });
+                            if (++i <= last) {
+                                next();
                             }
                         });
+                    };
+                next();
+            });
         },
     });
 };