initial blame view
do not treat root commits as boundaries

These boundary commits start with a "^" and are not supported by
Dulwich.
handle refs with / properly, fixes #36

With this patch, Klaus handles git refs with a slash '/', e.g.
feature/foo correctly. The URL structure remains the same, but there is
no longer a difference in <rev> and <path>.

Any URL is bit by bit checked if it contains a valid ref:

    -> /klaus/tree/foo/bar/setup.py
    <- foo/bar/setup.py (no)
    <- foo/bar, setup.py (yes, foo/bar is a valid ref)

For URL reconstruction, url_for(view, ...), there are still `rev` and
`path` arguments. The view on the other hand, joins both parts to a
single URL (and splits them (again) into rev and path).

Tarball filenames for branches containing a slash are substituted with a
hyphen, so project@foo/bar becomes project@foo-bar.tar.gz
add documentation and remove superfluous path converters
Merge branch 'fix/36'
Merge remote-tracking branch 'origin/feature/git-blame'

Conflicts:
	klaus/__init__.py