As part of the cache purging changes added in 1e3beb6e9, we should ignore our query string so caching isn't bypassed.

Include post-password cookies in those exempt from caching, otherwise password-protected posts can end up in cache.

Fixes #6.

Fixes #5.

* Abstract Redis connection logic for reusability
* Abstract purging logic for reusability
* Create reusable purging logic
* Introduce single-page purging via the admin bar

See #5

Also fixed a bug that prevented invalidation of the homepage due to a missing trailing slash, and therefore mismatched keys.

Rather than check the request method, check for the presence of posted data upon which some script would have to act.

Include query strings when building cache keys, to avoid corrupting caches with data WP generates based on present query strings.

See #3.

See #3.

Fixes #3.

Fixes #4.

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

See #1.

See #3.

* Cache protocol-specific pages
* Ignore all query args and hashes, not just that used to clear a page's cache

Fixes #2.