[doc] Update README.md

Handle case where no files to cleanup exist.

This fixes cases where "*.foo" expands to the string "*.foo" if no matching files exist.

Pass intermediate cert to hook script

Use /usr/bin/env bash shebang

On FreeBSD bash is installed in /usr/local/bin; this patch
alters the shebang to use /usr/bin/env bash instead, to ensure
that the shell scripts work on (particularly) the *BSDs as well.

Skip non-folder entries on cleanup.

Updated Readme with rate limit warning + staging URL

There is currently no mention of Let’s Encrypt rate limits or the staging server. I’ve updated the readme so that the rate limit notice is prominently displayed and the necessary config setting to use the staging server is included in the instructions.

changed the way SCRIPTDIR is searched for so it works better with symbolic links (e.g. a symbolic link in ~/.bin)

Added LOCKFILE to config.sh.example

The dns-01 support is now available in production

pass IO descriptors to HOOK transparently

closes #101