Configured New Relic to load earlier in the process

refs https://github.com/TryGhost/DevOps/issues/68

- we want New Relic to be one of the first modules to load so it can
  instrument the rest of our code
- previously this would not have been the case, and it would have missed
  out on instrumenting the config and logging code
- this moves the require to be the first step in the process if the
  PRO_ENV env var is set

ghost/core/core/boot.js

@@ -477,13 +477,6 @@ async function bootGhost({backend = true, frontend = true, server = true} = {})
     try {
         // Step 1 - require more fundamental components
 
-        // Load New Relic
-        debug('Begin: Load New Relic');
-        if (config.get('newRelic:enabled')) {
-            require('newrelic');
-        }
-        debug('End: Load New Relic');
-
         // Sentry must be initialized early, but requires config
         debug('Begin: Load sentry');
         require('./shared/sentry');

ghost/core/index.js

@@ -1 +1,6 @@
+// Load New Relic
+if (process.env.PRO_ENV) {
+    require('newrelic');
+}
+
 require('./ghost');