More caching

[Gaurav0]

Currently the process of generating a db takes a very long time. We are caching downloaded builds, which prevents us from downloading again, but would it be possible to cache generated CouchDb documents to avoid redoing the expensive markdown to html conversion? These could be saved to json files and invalidated manually by deleting the temporary directory they are placed in.

[sivakumar-kailasam]

We moved away from couch to s3 and there are some caching steps through out the tool that has improved incremental generation.