Remove catch-all rescue in Driver.for_plugin (let me explain!).

Previously this method had 3 things to do:

1. call a require
2. determine the correct constant for the driver class
3. instantiate an driver object, passing in an options hash

Now there is optional driver dependency logic that is being executed and
in short, this method is less than trivial. Now we want to see the
uncaught exceptions bubble up.