docs: better documentation for caching

[Hectorhammett]

closes: #562

[bshaffer]

I suggest also adding an example of implementing a third party cache, for this example. Something like

Integrating with a third party cache

To increase performance, you can use a third party file cache (such as Symfony file cache).... (show example)

[bshaffer]

Much better! Some typos and then this is good to go