pkgme fails building a package that has a "-" in the version number

"-" is special in version numbers. If the package has a version number with a "-"
in it then pkgme fails to build the source package.

This is because it uses the whole version number in the .orig.tar.gz filename, but
debuild only expects it to have the version number with the last "-" and any subsequent
characters removed.

So 1.0-1 should have 1.0.orig.tar.gz, but pkgme generates 1.0-1.orig.tar.gz.

The debian.changelog.Version class can be passed the version string to create,
then the upstream_version attribute can be used.

Otherwise s/-[^-]*// should suffice.

We should also check similar requirements for epochs, and handle those
correctly too.

Thanks,

James