Implemented branch option for Git::Init

You can now specify the name of the branch to which the default Git
branch (master) is renamed after the initial commit.
Clean up github#21

  Use "git checkout -b" instead of renaming branch after commit.
  Log after commit (and mention branch if non-default)
v2.024

 - add branch option to Git::Init (tuomas jormola - github#21)
 - Git::Init now logs when it makes the initial commit