Update readme contributing section

* Allow for UDP servers

Extend the Server interface with ServePacket and ListenPacket - this is
in the same vein as the net package.

Plumb the packetconn through the start and restart phases.

Rename RestartPair to RestartTriple as it now also contains a Packet.
Not that these can now be nil, so we need to check for that when
restarting.

* Update the documentation

fix: import should always be relative to current file directory

fix transparent host header #916

* import should get absolute path before glob

* fix test: import should get absolute path before glob

* try to fix test on windows

* use complete path as the dispenser filename

* fix caddyfile test

* Prototype middleware Config

* Refactors

* Minor refactors

discard remaining args for if block in redir.

fix rewrite if problem (skip remaining args)

* Initial concept for pluggable storage (sans tests and docs)

* Add TLS storage docs, test harness, and minor clean up from code review

* Fix issue with caddymain's temporary moveStorage

* Formatting improvement on struct array literal by removing struct name

* Pluggable storage changes:

* Change storage interface to persist all site or user data in one call
* Add lock/unlock calls for renewal and cert obtaining

* Key fields on composite literals

Changing refs from /usr/bin to /usr/local/bin

Thanks to @jaredfolkins for the feedback

Test that the host header forwarding on proxy

Support for placeholders in fastcgi env vars.

This is inconsistent with the other directives, but import is a special
case and frankly the behavior of import shouldn't change depending
on the directory from which you run caddy. Breaking change but I think
it's for the better, and best to do it now before 1.0.

Also see
https://forum.caddyserver.com/t/caddy-0-9-beta-version-available-updated-beta-2/146/29?u=matt
which has another account of strange proxy behavior; I think this
resolves that.