[refactor] Add Logger plugin

lib/forever/plugins/logger.js

@@ -0,0 +1,53 @@
+var Logger = module.exports;
+
+Logger.name = 'logger';
+
+Logger.attach = function (options) {
+  var self = this;
+
+  this.on('start', function () {
+    startLogging('stdout');
+    startLogging('stderr');
+
+    function startLogging(stream) {
+      self.child[stream].on('data', onData);
+
+      if (options[stream]) {
+        self[stream] = options[stream]
+      }
+
+      function onData(data) {
+        if (!self.silent && !self[stream]) {
+          //
+          // If we haven't been silenced, and we don't have a file stream
+          // to output to write to the process stdout stream
+          //
+          process[stream].write(data);
+        }
+        else if (self[stream]) {
+          //
+          // If we have been given an output file for the stream, write to it
+          //
+          self[stream].write(data);
+        }
+      }
+
+      function stopLogging() {
+        if (self[stream] && !options[stream]) {
+          //
+          // Close the stream only if it wasn't provided in `options`. If it was,
+          // caller is responsible for closing it.
+          //
+          self[stream].close();
+        }
+      };
+
+      self.on('exit', stopLogging);
+    }
+  });
+};
+
+Logger.init = function (done) {
+  done();
+};
+