Adds Boston MBTA API to Transportation

The Boston MBTA API provides easy access to MBTA schedules, alerts, and real-time transit information.

README.md

@@ -828,6 +828,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Amadeus Travel Innovation Sandbox](https://sandbox.amadeus.com/) | Travel Search - Limited usage | `apiKey` | Yes | Unknown |
 | [Bay Area Rapid Transit](http://api.bart.gov) | Stations and predicted arrivals for BART | `apiKey` | No | Unknown |
 | [BlaBlaCar](https://dev.blablacar.com) | Search car sharing trips | `apiKey` | Yes | Unknown |
+| [Boston MBTA Transit](https://www.mbta.com/developers/v3-api) | Stations and predicted arrivals for MBTA | `apiKey` | Yes | Unknown |
 | [Community Transit](https://github.com/transitland/transitland-datastore/blob/master/README.md#api-endpoints) | Transitland API | No | Yes | Unknown |
 | [GraphHopper](https://graphhopper.com/api/1/docs/) | A-to-B routing with turn-by-turn instructions | `apiKey` | Yes | Unknown |
 | [Icelandic APIs](http://docs.apis.is/) | Open APIs that deliver services in or regarding Iceland | No | Yes | Unknown |