Fix ruby-growl adapter to work with new Growl protocol

At some point, Growl has changed their protocol methods, and `ruby-growl` has been [updated](https://github.com/drbrain/ruby-growl/commit/c9ca7e88313e84a2c16d7d3e3a6fe5626fa7bff1) as well. This commit resolves a protocol error that was causing the `earthquake` gem to fail on launch after a clean install.