Add trip_duration method
Add power source method to Train class
Merge remote-tracking branch 'origin/master' into calculate-trip-time

Conflicts:
	train.rb
Fixing Bug
Merge pull request #1 from clamstew/calculate-trip-time

Calculate trip time
Add a method to the Train class to calculate the distance based on the duration
Squashed commit of the following:

commit 6cce32f6a3ea6eb70d3e4edb5c6edef24993d1ca
Author: Clay Stewart <claytonmstewart@gmail.com>
Date:   Fri Sep 20 14:25:23 2013 -0500

    Add a method to the Train class to calculate the distance based on the duration
Add a method to calculate trip distance.

[Closes #2]
Remove line
Merge pull request #3 from clamstew/2-add-trip-distance

Add a method calculate the distance
Merge pull request #4 from clamstew/master

Merge add building