Add a mechanism for caching queries

[nickpalmer]

In a SPA if I navigate back Kasia shouldn't have to re-run the queries to build the page.

[nickpalmer]

This probably needs some way to specify a 'cache-key' and an expiration time as a portion of the API. Maybe an optional third function to the connect calls that returns those values?

[sdgluck]

It might be possible by creating an "intercept transport" for the node-wpapi library that does something like hashing the final request URL and storing that as the cache-key. Before each request is fired, we check if the hash is different. Something like that?

[MickeyKay]

We have a similar need, and are likely going to try to integrate node-redis into that transport method. I believe this is the prescribed approach. Here's an example for reference: https://github.com/WP-API/node-wpapi#customizing-http-request-behavior

[MickeyKay]

Somewhat related: #77