Add a redis adapter to this library

[KenEucker]

To store the data from Imgur, and reduce the number of calls being made to Imgur overall, we should add a redis store that can be used as the backbone for the 'biketag' source. To implement this, a flag for whether or not to pull data from Redis should be ingested in the payload. If that flag is present, then there should also be a mechanism for updating data when it has become stale from another source (imgur).

[KenEucker]

This may no longer be a necessary issue, as the flat json files used by the new aws adapter might be good enough for a while.

However, implementing a redis layer for caching may become useful in the future, given that the only json data we are storing is tag data. If it comes to an issue with the biketag api endpoints that can't process that data in less than 10 seconds and send it out, then we might be back to needing this.

Leaving this issue open for now.