Don't install tests

The OWSLib package, when installed from pypi installs a directory tests. This is due to the find_packages in setup.py, which also find the tests directory. Because the tests directory includes an __init__.py, find_packages thinks tests is also a package and installs it. By excluding the tests directory from the find_packages, it is no longer installed. 
I also added the other directories that are probably not meant to be packages.