Fixup example.

[dblock]

Makes the example run (fix relative path to 23.tcx) and output something a little more readable.

$ bundle exec ruby examples/basic_run.rb 

Distance meters: 134500.77
Time seconds: 15496.0
Calories: 3245
Total ascent: 1528.00048828125
Total descent: 1527.2004699707031
Max altitude: 666.2000122070312
Average heart rate: 0.0
Average watts: 226.8091263216472
Max watts: 587.0
Average speed: 9.337573943138288
Average speed (moving): 9.34212283433475
Average cadence (moving): 82.03661343691554
Average cadence: 79.33173344462993