Add a more proper SPEC file

This makes some changes to obsolete the create-rpm script, which is against
the concept of RPM building.

Most notable changes:
- Use the original source tarball from github.
- Provide a downloadable URL which creates the correct file name (at least
  when using spectool).
- Use more macros (a lot of them).
- BR ronn for building the documentation from markdown.
- Create the documentation and package it as HTML.
- Make %setup quiet.
- Don't install q twice (minor bug in original SPEC).
- Preserve modification dates.
- Don't compress man page explicitly (RedHat's and Fedora's packaging
  process does that).