Added configuration option to disable queue instrumentation

[asgrim]

Part of #43

Todo

• [x] Merge scoutapp/scout-apm-php#156
• [x] Rework this PR to use the new disabled_instruments configuration

[cschneid]

For parity w/ ruby and flexibility later to turn on & off instruments, can we have a more general config: disabled_instruments

https://docs.scoutapm.com/#disabled_instruments

In Ruby, it's the name of classes, but it can be text names instead. laravel_queues and so on.