Web content sanitizer proxy as a service.

Morty rewrites web pages to exclude malicious HTML tags and attributes. It also
replaces external resource references to prevent third party information leaks.

The main goal of morty is to provide a result proxy for searx, but it can be
used as a standalone sanitizer service too.

Features:
* HTML sanitization
* Rewrites HTML/CSS external references to locals
* JavaScript blocking
* No cookies forwarded
* No referrers
* No caching/etag
* Supports GET/POST forms and IFrames
* Optional HMAC URL verifier key to prevent service abuse
