Automate UPDATING process

[barbeau]

Currently each time the canonical gtfs-realtime.proto changes, we need to go through a manual process for each language to update the bindings:

• .NET
• Golang
• Java
• NodeJS
• Python

We should automate this process.

Some resources:

• Java - Example of using protobuf-maven-plugin to automatically invoke protoc as part of the build process - Use protobuf-maven-plugin to compile extensions automatically OneBusAway/onebusaway-gtfs-realtime-api#17

[kurtraschke]

FYI, protobuf-maven-plugin can also build bindings for C++, C#, JavaScript, and Python, although I'm not sure how useful it is to have bindings for those languages end up in a Maven artifact, when they really need to get packaged and submitted to their respective languages' package repositories (although that could always get hacked into the Maven build process somehow...).