Kata: Going functional in Python

Description

Kata in python suggested by my friend Edorka.

I've to code a functional program in python that compress a string by replacing each line of repeated characters by the current char and the number of times it appear, this way: asssdff would become as3df2.

Kata rules

1. I can't use array functions
2. I can't use variables
3. Each function must begin with a return statement
4. I must apply TDD

To run

$ nose2 --with-coverage