Resolve undefined index notice
Update debugging messages slightly.
Improve cache key generation

* Cache protocol-specific pages
* Ignore all query args and hashes, not just that used to clear a page's cache
Remove a seemingly unnecessary check on the request, which broke processing of POST requests.
Rename plugin to Redis Page Cache
Remove errant backquote introduced in e6faa20f5
Update more instances of the old plugin name
When retrieving settings from options, overwrite global values so everyone's on the same page. :)
Correct configuration name changed in a95e5255f, but missed in this instance.
Allow versioning of caches for plugin upgrades.

See #3.
Improve debugging messages and reduce duplication. Many of these came from the original plugin this is forked from.

See #1.
Add static caching to URL building method to reduce burden of calling it multiple times.

Fixes #4.
Add default support for `Last-Modified` and `Cache-Control` headers.

Fixes #3.
Better code organization and some inline comments for the changes from 19d6f1.

See #3.
Capture additional headers, and allow others through via a whitelist.

See #3.
Output content encoding headers for happy receipients