Add ability to skip merges in Repository#log

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Remove GitStats, LogParser and Stats classes

They are not generic and depends deeply on graphs implementation inside
GitLab. So keeping them in library does not makes sense. In order to
implement graphs in GitLab we can just use Repository#log. No need to
have such duplication in code with strange parsers

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Dont require non-existing classes

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
New version

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'cleanup' into 'master'

Cleanup gitlab_git

Remove GitStats, LogParser and Stats classes.

They are not generic and depends deeply on graphs implementation inside
GitLab. So keeping them in library does not makes sense. In order to
implement graphs in GitLab we can just use Repository#log. No need to
have such duplication in code with strange parsers

See merge request !10