Tito 0.6.27

• #507 - Defer submodule detection to git to prevent fails caused by empty .gitmodules file
• Many improvements to tests and they now run during package build
• #460 - Sometimes Tito-built packages have lower NVR than packages from the official repositories. This can now be prevented by
  new config option buildconfig.test_version_suffix. It can be used like this:

$ cat .tito/tito.props
[buildconfig]
test_version_suffix = .tito.git

Thank you @abn and @praiskup for contributing to this release.

PS: The release commit and tag were done by "unknown user". Sorry about that, it was me (@FrostyX), something messed up my ~/.gitconfig.