PHP Warning fix + extraParameters from config

1. Fixed PHP Warning: If we're using Resque - we are almost guaranteed to load it ourselves in order to configure it. Since `class_exists()` tries to autoload by default, this raises a PHP Warning every time an exception is handled. Setting `$autoload=false` on the parameter list makes sure it only tests for already existing Resque, not attempt to include it as well.
2. You can now include 'extraParameters' in your configuration as well and it will be sent to Airbrake's "parameters" field (used to have to be hard coded?)