layman.xml: add email, replace ssh uri with git://

* add email addr to <owner>
* when trying to add the overlay:

>  LANG=C LC_ALL=C layman --nocolor \
>    --overlays='https://raw.github.com/xp-vit/tlp-portage/maint/layman.xml' \
>    -a tlp
>>
>>   * Adding overlay,...
>>   * Running Git... # ( cd /var/lib/layman  && /usr/bin/git clone
>>   git@github.com:dywisor/tlp-portage.git /var/lib/layman/tlp )
>>  Cloning into '/var/lib/layman/tlp'...
>>  Permission denied (publickey).
>>  fatal: Could not read from remote repository.
>>
>>  Please make sure you have the correct access rights
>>  and the repository exists.
>>   * Failure result returned from Git
>>   * Running Git... # ( cd /var/lib/layman/tlp  && /usr/bin/git config
>>   user.name "layman" )
>>   * [Errno 2] No such file or directory: '/var/lib/layman/tlp'
>>   *
>>   * Trying next source of listed sources...
>>   * Running Git... # ( cd /var/lib/layman  && /usr/bin/git clone
>>   https://github.com/dywisor/tlp-portage.git /var/lib/layman/tlp )
>>  Cloning into '/var/lib/layman/tlp'...
>>  remote: Counting objects: 392, done.
>>  remote: Compressing objects: 100% (211/211), done.
>>  remote: Total 392 (delta 154), reused 378 (delta 140)
>>  Receiving objects: 100% (392/392), 98.16 KiB | 0 bytes/s, done.
>>  Resolving deltas: 100% (154/154), done.
>>  Checking connectivity... done.
>>   * Running Git... # ( cd /var/lib/layman/tlp  && /usr/bin/git config
>>   user.name "layman" )
>>   * Running Git... # ( cd /var/lib/layman/tlp  && /usr/bin/git config
>>   user.email "layman@localhost" )
>>   * Successfully added overlay(s) tlp.

=> replace ssh uri with git