Checking the London Tube Status with Vonage's SMS API

This application allows users to check the status of a given line on the London Underground by sending an SMS with the line name. The application uses the Vonage SMS API and the Transport for London (TFL) API to retrieve real-time data about the status of the tube line chosen by the user. When an inbound message is received, the application checks if the line name matches any of the valid values in the `lines` array. If it does, the application sends a message back to the user with the current status of the line. Otherwise, it sends a message providing the valid values. The application can be deployed to Heroku, where it will scale according to traffic demand and consume dyno hours only when running.