Added routes() function to create MultiLineString geojson

[AvidDabbler]

I was looking for a good solution for simply and performantly creating routes MultiLineString geojson and I came across your repo.

I added a function called routes() that finds all of the trips in a route, gather all of the shape_id's and loops through each of the shapes to see if it needs to be added to the route MultiLineString geojson file.

I tried to follow the pattern that you all set by loading the csv file prior, then parsing in the function. The routes function does need 3 different files in order to work though (routes, trips, and shapes).

I updated the routes.input file and added the trips and shapes files in the testing folder and added the routes() to the testing script.

Seems to all be passing. :D

[AvidDabbler]

if you need me to make the input and geojson files smaller in test I can try to take a look at that this week