Calculate the distance between two towns along the Cotswold Way

Set the co-ordinates of two towns along the Cotswold Way and run distance.py to output the distance along the Way in kilometres

I've extracted the waypoints for the 'rte' element with the name 'Cotswold Way'. There are two others in the original file called 'Cotswold Way Loop 1' and 'Cotswold Way Loop 2' that I have ignored.

Data source: http://www.nationaltrail.co.uk/gpx_download?filename=national_trails_cotswold_way_2014.gpx Difference between two co-ordinates: http://www.johndcook.com/python_longitude_latitude.html