make the configuration file optional by scanning for `.conf` files in the current directory.

Now just `mirari build` works great, as long as there's one config file in the directory.
update README
Merge branch 'master' of github.com:avsm/mirari
Merge pull request #1 from avsm/master

working xen mirari
Update README.md
[make] eol
[main] remove spurious opam line from help