Build a manpage using Sphinx

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Merge branch 'manpage'

see pull request #72
minor manpage fixes

version numbers should be taken from the package automatically,
manpage building needs sphinx >= 1.0

The version number in the manpage is still always 1.1
on my system (sphinx 1.1.3, docutils 0.11) for unknown reasons.