Support for searching recursively

[Sentient07]

Suppose my codebase is of this structure, it'd be nice to recursively run the script for all the .py files.

• src/
  • driver.py
    • DB/
      • DBHelper.py
      • Analyze/
        • file1.py
        • file2.py
      • Helper/
        • HelperClasses.py

[xZise]

Shouldn't flake8 already do it? The stand alone feature is basically just a gimmick to easily test/use it without requiring flake8. So this is a bit low priority.