Changed repo structure for proper install and tests

cpopen.so used to be installed (when doing python setup.py
install) in site-packages instead of site-packages/cpopen.

This patch fixes that by making cpopen.so part of the cpopen
package, which also simplifies the spec file.

It also moves the tests into their own directory for better
organization.

Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>