In order to generate the current dropsonde ruby binding, do the following:

Ensure you have the latest dropsonde-protocol repository downloaded.
This can be found at https://github.com/cloudfoundry/dropsonde-protocol.git

Ensure you have the ruby_protobuf gem installed

Change to the directory where you want generated output

Invoke the rprotoc command to generate the ruby bindings.
Example:  rprotoc -p /home/user/workspace/dropsonde-protocol/events/ /home/user/workspace/dropsonde-protocol/events/envelope.proto