Update README.md with alternatives to using GitHub
Update README.md with alternatives to using GitHub

Some people don't like github. Make it clear that using the
mailing list for patches or bug reports is ok too.

Signed-off-by: Andy Grover <b7d524d2f5cc5aebadb6b92b08d3ab26911cde33@redhat.com>
mulkieran/stratisd,mulkieran/stratisd,trgill/stratisd,stratis-storage/stratisd,stratis-storage/stratisd,stratis-storage/stratisd,trgill/stratisd