Revert "Add new Python versions for testing"
Revert "Add new Python versions for testing"

The `format` method of string objects is a Python 3 feature that was only backported as far as Python 2.6. It was silly to even try to test anything older.

This reverts commit ecd91d76a6d8d3e492410932dd442442887c330f.

dirn/When.py