Revise pagure.spec to simplify and unify dependency lists
    
    This change reflects the actual dependencies of pagure and its subpackages
    to how it actually functions, and also gives us the benefit of easily
    switching the whole application to Python 3 in the future, when all the
    components are ready.
    
    Signed-off-by: Neal Gompa <ngompa13@gmail.com></ngompa13@gmail.com>