Clean up Beer.ontap method

- Don't select join fields when you can use the associations directly, otherwise you create fields that won't exist in other parts of the app. If outputting a particular specific JSON format in another part of the app do it there instead (i.e., controller or service class)
- Don't redefine the markup constants in another place in the select, that WILL lead to bugs down the road
- Only `include` brewers, not join, so that Rails can do it's own magic.