Offline: Persist posts data - wp-rest-api-sync

[rralian]

We have two potential approaches to caching... one in the calypso application via something like redux middleware, and one in a proxy service for the api. We should try both for this posts case and bump into the corners to see which approach seems the most immediately promising.

This task is to implement persistence for the posts-list data via the wp-rest-api-sync approach.

[rralian]

Closing this as we are planning to persist data in the redux store.