Process! is not propagating Beaneater::NotConnected exception.

As mentioned in the title, the process! method does not propagate or break from the while loop when there is Beaneater::NotConnected exception i.e when the Beanstalkd goes down.

Steps to reproduce:
1. Start beanstalk: `beanstalkd -l 192.168.50.21 -p 11300 &`
2. Put messages to the queue.
3. Start the consumer.
```
@beanstalk = Beaneater.new('192.168.50.21:11300')
begin
@beanstalk.jobs.register('my-tube') do |job|
puts "Job: #{job.inspect}"
end
@beanstalk.jobs.process!({:reserve_timeout => 10})
rescue Exception => e
puts "Exception: #{e.inspect}"
@beanstalk.close
end
```
4. Stop the beanstalk server.
5. The consumer is now hung as the process! method keeps retrying considering Beaneater::NotConnected as a StandardError.

Start with the `process!` method and trace how it handles `StandardError` and `Beaneater::NotConnected`. The issue’s reproduction steps show how to trigger the failure by stopping beanstalkd; done means `process!` no longer hangs retrying and allows the connection exception to propagate.

Written by the indexing model from the issue text.