jQuery should be required before turbolinks in manifest

Turbolinks documentation states that page:update is triggered on
jQuery's ajaxSuccess event, but this feature only works if jQuery is
loaded  before turbolinks. Make this load order requirement clear in
the installation instructions.
url attribute in pageCache is not used and is incorrect when the back button is used
Change cache key to be url instead of state position
Reflect url immediately upon visit. No need to call rememberCurrentUrl() on xhr.abort
Display a cached copy of a page if available before fetching its replacement
Constrain the cache size by removing the oldest caches
Add an opt-out for transition cache
Disable transition cache by default. Allow opt-in via Turbolinks.enableTransitionCache()
Add back the url attribute in pageCache
Add documentation for transition cache
Merge pull request #286 from smidwap/transition_cache

Transition cache
Merge pull request #323 from mbrictson/turbolinks-after-jquery

jQuery should be required before turbolinks in manifest
Added PHP port
Merge pull request #325 from carlalexander/patch-1

Added PHP port
Release transition cache - v2.2.0
Do not store redirect_to location in session if the request did not come from Turbolinks - Closes #317