add ability to ignore some URLs

[brettmc]

Is your feature request related to a problem? Please describe.
In a setup where we have health checks pinging our PHP services, I would like to not have all of those microtransactions instrumented by APM. In my case, it's a php-fpm check which hits pm.status_path = /status directly:

"REQUEST_URI=/status HTTP_HOST=${HOSTNAME} REQUEST_METHOD=GET SCRIPT_NAME=/status SCRIPT_FILENAME=/status /usr/bin/cgi-fcgi -bind -connect localhost:9000"

Describe the solution you'd like
I'd like to see ELASTIC_APM_TRANSACTION_IGNORE_URLS implemented, along the lines of the nodejs implementation:
https://www.elastic.co/guide/en/apm/agent/nodejs/current/configuration.html#transaction-ignore-urls
I would then like to set ELASTIC_APM_TRANSACTION_IGNORE_URLS=/status,/ping etc, and have those URLs not instrumented automatically.

Describe alternatives you've considered
If I could run some userland code, I'd $transaction->discard(), but an fpm status page only triggers built-in/pre-load code (bootstrap_php_part.php)

[adamtester]

This is actually already implemented, but not in a release yet, see:
dc89ad2

In the meantime you can use dev-master in composer

[brettmc]

Confirming that this is a duplicate of #82, and the implementation in master looks like what I need. Closing.