Squashed commit of the following:

commit 8de1e047bde0909b6758d269e8c0b73d75a65428
Author: Kendra McClanahan <kendramcclanahan@kendras-mbp.att.net>
Date:   Fri Dec 6 12:11:19 2013 -0600

    COMMENTS

commit 2071c5f997549918cc387e2bdbf7e4ac99efec48
Author: Kendra McClanahan <kendramcclanahan@kendras-mbp.att.net>
Date:   Fri Dec 6 12:07:44 2013 -0600

    Add trip_distance method to Train class