feat(logging): Add logging-setup function

Add a setup-function for setting up the log-level and colors from config.

lib/logger.js

@@ -43,6 +43,29 @@ var setup = function (level, colors, appenders) {
   })
 }
 
+// Setup the logger by passing in the config object. The function sets the
+// `colors` and `logLevel` if they are defined. It takes two arguments:
+//
+//     setupFromConfig(config, appenders)
+//
+// * `config`: *Object* The configuration object.
+// * `appenders`: *Array* This will be passed as appenders to log4js
+//   to allow for fine grained configuration of log4js. For more information
+//   see https://github.com/nomiddlename/log4js-node.
+var setupFromConfig = function (config, appenders) {
+  var useColors = true
+  var logLevel = constant.LOG_INFO
+
+  if (helper.isDefined(config.colors)) {
+    useColors = config.colors
+  }
+
+  if (helper.isDefined(config.logLevel)) {
+    logLevel = config.logLevel
+  }
+  setup(logLevel, useColors, appenders)
+}
+
 // Create a new logger. There are two optional arguments
 // * `name`, which defaults to `karma` and
 //   If the `name = 'socket.io'` this will create a special wrapper
@@ -60,3 +83,4 @@ var create = function (name, level) {
 
 exports.create = create
 exports.setup = setup
+exports.setupFromConfig = setupFromConfig