[BUGFIX] #5 Fixed RepositoryCommandError on empty git repository

If an empty git repository (without any commits) will be analyzed
repositoryhandler fails because the command
git log --all --topo-order --pretty=fuller --parents --name-status -M -C --decorate=full origin
fails with exit code 128
Fix error #7: Error when parsing Git version with chars
Gitref argument to backends log method.
Merge branch 'pr/6'
implemented is-ancestor for git 1.8+
is_ancestor taking one more parameter
[TASK] Renamed README to README.md to support Markdown syntax
Reformat README.md to make usage of Markdown elements
Renamed NEWS to NEWS.md
Make usage of Markdown in NEWS.md
PEP8 compliance
Added .idea t .gitignore file
Merge pull request #11 from linzhp/feature/is_ancestor

implemented is-ancestor for git 1.8+
Merge pull request #12 from andygrunwald/readme-md

Reformat README to make usage of Markdown elements
Merge pull request #13 from andygrunwald/news-md

Reformat NEWS to make usage of Markdown elements
Merge pull request #14 from andygrunwald/pep8

PEP8 compliance
Merge pull request #15 from andygrunwald/pycharm

Added .idea to .gitignore file to work with PyCharm IDE
Add '--remotes' param to log command for Git >= 1.8 versions
Merge pull request #4 from linzhp/master

Added size watcher
Add -c option to git-log