Improve Administrator Panel

![adminpanel](https://cloud.githubusercontent.com/assets/8646429/5247704/cd13751c-7942-11e4-8900-5966f2a06cb4.gif)

Unused block argument - `availability`. If it's necessary, use `_` or `_availability` as an argument name to indicate that it won't be used.<br>Space between { and | missing.<br>Space missing inside }.