Play 2.3: use onLoadConfig instead of totalConfiguration

[markusjura]

To use the ConductR configuration in Play 2.3 the README currently suggests to override the configuration method:

import play.api._
import com.typesafe.conductr.bundlelib.play.Env

object Global extends GlobalSettings {
  val totalConfiguration = super.configuration ++ Configuration(Env.asConfig)

  override def configuration: Configuration =
    totalConfiguration
}

This should be changed towards overriding the onLoadConfig:

override def onLoadConfig(config: Configuration, path: File, classloader: ClassLoader, mode: Mode.Mode) =
  config ++ Configuration(Env.asConfig)

This was a suggestion by @gmethvin.