Add unit tests for distance calculator
Add unit tests for distance calculator

These first tests check the control flow in the part of the distance
calculator that determines the scale of the movement and checks the
result against a pattern for the 3 scales:

 * kilometres
 * metres
 * negligible (<5m)

Currently the test for metres fails because the output contains a
decimal point even though it's supposed to be an integer, anyway TDD is
supposed to start with a failing test! ;-)

sinisterstuf/youmoved,sinisterstuf/youmoved