Added gitignore, requirements.txt and the results folder

Hi,

Interesting paper, I definitely need to spend some more time reading it.  

I added some things to the repository to make it easier to use, like:
- a gitignore which prevents some files from being added to the repository,
- requirements.txt which has a list of python packages that people need to run the code.
     You can type 'pip install -r requirements.txt' to install them all.
- I put a placeholder in the src/results folder because it doesn't get created otherwise when you check it out.

Hope that helps.

Regards,

Paul