Major changes to setup.py

1/ Now requires 'setuptools'
2/ Installs documentation as well as example files
3/ Creates 'entry point' scripts for common pywws commands
4/ No longer installs scripts from 'scripts' directory
5/ Adds dependencies, for things that are in PyPI

If you use local sources of pywws (archive download or repos clone) you
can install the entry point scripts with 'python setup.py develop'. You
also use pip to install with 'pip install -e .' (note the '.' for
current directory).