Add improvements to podcast types. [Set default type to most popular type for that podcast ] #14
Description
Currently all podcasts default to normal type unless the user has specified their own value.
Each podcast type should default to the most common type of subscription for that podcast. This value should be cached and not calculated each time the podcast type is requested.
A podcast_type attribute could be added to podcasts, and a rake task can be written set each podcast's podcast_type to the most popular subscription type.