Ruby script that takes a directory containing GoogleTracks kml files and:
1) Presents a 'start' date (the earliest date contained in the kml files)
2) Presents a 'end' date (the latest date contained in the kml files)
3) Presents a Summary of activities:
    3a) Total Number of Activities
    3b) Total Miles
    3c) Average Total Pace
    3d) Total Number of Walks (also show percentage of walks in total activities)
    3e) Miles Walked
    3f) Walking Pace
    3g) Total Number of Runs (also show percentage of walks in total activities)
    3h) Miles Ran
    3i) Running Pace