create data structure for subway system

* Create a hash to represent the entire subway system
* Create hash entries using the line (red, green, orange) names as symbols/keys and the values are arrays with the associated stops listed in order.
add prompts to get user input

* prompt for origin line/stop

* prompt for destination line/stop

* user input is saved in a variable, chomped, and downcased
use user inputs to calculate stop distance on same line

* use .index to access the index location of the stop on the particular line

* subtract origin index from destination index and use the absolute value as the number of stops
find the distance between two stops on different lines

* create equations to compute the number of stops from origin stop to intersecting station and from interecting station to destination stop.

* add these equations together for the number of stops for a change of lines
make changes

* make changes to input section to give error messages for invaid inputs

* attempts at making egde cases using if elsif statements (not successful)
makes some style adjustments