See http://sourcefrog.net/projects/natsort/ for details of the original
implementation. This varient is exactly the same except written in python.
Consider it licenced under the same licence as the original C code by
strnatcmp.strnatcmp and the case insensitive equivalent strnatcmp.strnatcasecmp
which can be used within python to sort strings that may start and end with
numbers in a more natural fashion that a basic sort will, i.e with strnatcmp
9foo appears before 10foo and foo9 appears before foo10.
Caolan McNamara (2003) <email@example.com>