Adds tests for both the path matcher and host matcher for case
insensitivity.
If case sensitivity is required for the path, a regexp matcher can
be used instead.
This is the v2 equivalent fix of PR #2882.
- Fix static responder so it doesn't replace its own headers config,
and instead replaces the actual response header values
- caddyhttp.ResponseRecorder type optionally buffers response
- Add interface guards to ensure regexp matchers get provisioned
- Use default HTTP port if one is not explicitly set
- Encode middleware writes status code 200 if not written upstream
- Templates and markdown only try to execute on text responses
- Static file server sets Content-Type based on file extension only
(this whole thing -- MIME sniffing, etc -- needs more configurability)