Ask for the user's line!
Erase previous stuff. Set up charlie map.
Add user-input mechanism
Add way for user to input destination information as well
Measure distance between two stops on the same line.

* Only executes if the user gives two stations on the same line!
Add support for origins/destinations on different lines

* Calculate distance from startpoint to transfer station
* Calculate distance from transfer station to endpoint
Add auto-detect for transfer stations

* If all lines converge at more than one stop, OFF WITH YOUR HEAD
Add a method that calculates distance of a particular leg

* is this measurably better? it's not clear!
Clean up commented out bits (from before I had written the method)
Add cute messages at the end telling you what to do