Add distutils installation script. Closes #2

This adds a setup.py distutils module that simplifies the tasks of distributing and installing the program. I have removed the .py extension from the script name, as now that it is going to be started from the command line the user should not be constantly reminded in which language the script is written.

The installation instructions in the README have also been updated. The process now only requires the user to download the source code and execute `python setup.py install`, but I have detailed all the command-line steps so that those that do not know how to do that can simply copy and paste them in their terminal.