civi crm get request not working
Please post the full url you call, but you probably have an error on the url, it should have an action=get (or getcount or get*) param. If it doesn't, it blocks the access, because it doesn't know it's a read only action that can actually be performed over a GET method

However, as Jaap mentioned, I would recommend you to use POST all the time, no matter the action you want to perform, it's easier and cleaner.

FYI, in my client libraries, I tend to have the action+entities as get param and all the rest into post. The main reason is that it's giving cleaner logs to help understand what's going on, without leaking any sensitive information

Please share if you write a gem to wrap up the rest call inside a ruby framework, I'd be interested to use it on one of my project (sinatra, but probably going to work the same)