Handle undefined redis_version

Apparently some servers don't send the redis_version with the INFO command (*cough* redis cloud *cough*). This causes the app to crash violently (yay node!).

index.js

@@ -378,9 +378,11 @@ RedisClient.prototype.on_info_cmd = function (err, res) {
     });
 
     obj.versions = [];
+    if( obj.redis_version ){
         obj.redis_version.split('.').forEach(function (num) {
             obj.versions.push(+num);
         });
+    }
 
     // expose info key/vals to users
     this.server_info = obj;