Use select2 for town forms

https://trello.com/c/ZdjvHBMP/18-select2

![select2](https://cloud.githubusercontent.com/assets/8646429/5185217/8bba0d76-748b-11e4-8c80-d3c18e528c9f.gif)

All of these can be in one function:

```javascript
$(document).ready(function(){
  $("select#presence_town_id").select2();
  $("select#availability_town_id").select2();
  // ....etc....
});
```