Add stale-while-revalidate support with on_stale refresh hook#139

matthutchinson wants to merge 1 commit intosourcelevel:mastersourcelevel/faraday-http-cache:masterfrom

matthutchinson:support-stale-while-revalidate-async-cache-refreshingmatthutchinson/faraday-http-cache:support-stale-while-revalidate-async-cache-refreshingCopy head branch name to clipboard