redir: Preserve query string on catch-all redirect (fixes #180)

Use path.Join and then check if the request had a slash at the end to
place it again.

Used http status code instead of a hardcoded value.
Used url.Parse instead of url.ParseRequestURI, so that you can parse
both absolute and relative URL.

The get parameters are now forwarded when redirected.
Added some tests to validate this behavior.

Complete test coverage for config/setup/markdown.go

ext: Initial tests for the extensions middleware

gzip: Const for wildcard extension (and added test)

gzip: Make it gzip again

Removes mimes filter in favor of extensions filter (might be temporary)

preliminary test case for config/setup/markdown.go

git: Remove from core (available as add-on)

i.e. included files are also parsed as templates

Massage some verbiage

fastcgi: Fix for Issue 141: index not found, 502 Bad Gateway.

The grammar felt off on the sentence I changed. You can take or leave this PR, I won't be offended if you dislike my suggestion.

Complete test coverage for config/setup/templates.go

Decouple git middleware from caddy core. Now available as an add-on at https://github.com/abiosoft/caddy-git.