Bring into PEP8 compliance and a few Pythonic tweaks

This pull request will:
- Format the file using PEP8 guidelines (http://legacy.python.org/dev/peps/pep-0008/)
- Update the .gitignore to ignore the download directory
- Use the new style string formatting for readability purposes
- Use the os.path.join to safely create paths on different operating systems
- Use enumerate() to get an index of which file we are downloading