Updated ServeHTTP comment to indicate that it is 
setting headers and not adding them to existing values.

redirect: initial test for Redirect

Removed body check and replaced urlPrinter with a inlined Next handler

Ensures metadata.Variables is made

Markdown: support for templates and metadata

Close #64 (Make it possible to remove headers)

Adding "internal" middleware

- Detect too many internal redirects - return 500 in this case

- redirect internally regardless of proxy status code
- support multiple internal redirects