Merge pull request #2 from mapleoin/master

sure
only update the main package's .changes file
fix Version parsing from spec file
fix first run as different from no changes

If there are no changes, the .spec file should not be updated so as not
to change the timestamp in the Version field. On the first run however,
we have to set the Version field to the specific format which
git_tarballs uses
more comprehensive README