Squashed commit of the following:

commit da637fcd55187379b00bcc7655048eeb58283790
Author: nicole pank <nicole.pank@gmail.com>
Date:   Fri Sep 20 14:58:39 2013 -0500

    Add end to trip_distance method

commit 113ea667809d8d6586278a0b6899e1e47ec8b050
Author: Bonnie <blmattson@gmail.com>
Date:   Fri Sep 20 14:51:20 2013 -0500

    add comments to trip_distance

commit d5c50bf97339ab2aefeb28205eafbbbae27bfb67
Author: Bonnie <blmattson@gmail.com>
Date:   Fri Sep 20 14:45:23 2013 -0500

    add trip distance method