Merge package name/path and make them a positional argument

[Slavek Kabrda]

...meaning that pyp2rpm foo or pyp2rpm path/to/package.tar.gz should work instead of using -p or -n. This change should make it to a new major release, since I think it's a major change from user POV.

[Robert Kuska]

Use argument instead of option for providing package name/source file Use click instead of argparse fixes #25

→ <<cset 2011de7ff80b>>