Cleaner looking email adresses in readme.md

[yoeriH]

Making it so that email addresses in the readme md look like:
matz@ruby-lang.org

Instead of:

mailto:matz@ruby-lang.org

[nobu]

It doesn't look cleaner to repeat same content in brackets and parentheses, to me.
Isn't there a simple way to make the link to a relative path?

[nobu]

I meant such as [COPYING](COPYING).