title: UnsupportedClassVersionError on running play application with JDK 1.7
body: <p>Just now started learning Play framework for my project requirement and my project only build on <strong>JDK 1.7</strong> so I have downloaded <strong>Play 2.3.9</strong> version and created a sample project by typing <code>activator new</code>. Then moved into the sample project directory and executed <code>activator run</code>. Then I see JDk incompatible exceptions. Where I have to make the changes to handle this?</p>
  
  <p><strong>log:</strong></p>
  
  <pre><code>[info] Loading project definition from E:\workspace\play\first-app\project
  [info] Set current project to first-app (in build file:/E:/workspace/play/first-app/)
  java.lang.UnsupportedClassVersionError: com/typesafe/config/ConfigException : Unsupported major.minor version 52.0
          at java.lang.ClassLoader.defineClass1(Native Method)
          at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
          at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
          at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
          at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
          at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
          at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
          at java.security.AccessController.doPrivileged(Native Method)
          at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
          at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
          at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
          at com.typesafe.sbt.web.SbtWeb$$anonfun$com$typesafe$sbt$web$SbtWeb$$load$1.apply(SbtWeb.scala:535)
          at com.typesafe.sbt.web.SbtWeb$$anonfun$com$typesafe$sbt$web$SbtWeb$$load$1.apply(SbtWeb.scala:535)
          at scala.Option.fold(Option.scala:157)
          at com.typesafe.sbt.web.SbtWeb$.com$typesafe$sbt$web$SbtWeb$$load(SbtWeb.scala:549)
          at com.typesafe.sbt.web.SbtWeb$$anonfun$globalSettings$1$$anonfun$apply$1.apply(SbtWeb.scala:143)
          at com.typesafe.sbt.web.SbtWeb$$anonfun$globalSettings$1$$anonfun$apply$1.apply(SbtWeb.scala:143)
          at scala.Function1$$anonfun$andThen$1.apply(Function1.scala:55)
          at sbt.Project$.setProject(Project.scala:319)
          at sbt.BuiltinCommands$.doLoadProject(Main.scala:484)
          at sbt.BuiltinCommands$$anonfun$loadProjectImpl$2.apply(Main.scala:475)
          at sbt.BuiltinCommands$$anonfun$loadProjectImpl$2.apply(Main.scala:475)
          at sbt.Command$$anonfun$applyEffect$1$$anonfun$apply$2.apply(Command.scala:58)
          at sbt.Command$$anonfun$applyEffect$1$$anonfun$apply$2.apply(Command.scala:58)
          at sbt.Command$$anonfun$applyEffect$2$$anonfun$apply$3.apply(Command.scala:60)
          at sbt.Command$$anonfun$applyEffect$2$$anonfun$apply$3.apply(Command.scala:60)
          at sbt.Command$.process(Command.scala:92)
          at sbt.MainLoop$$anonfun$1$$anonfun$apply$1.apply(MainLoop.scala:98)
          at sbt.MainLoop$$anonfun$1$$anonfun$apply$1.apply(MainLoop.scala:98)
          at sbt.State$$anon$1.process(State.scala:184)
          at sbt.MainLoop$$anonfun$1.apply(MainLoop.scala:98)
          at sbt.MainLoop$$anonfun$1.apply(MainLoop.scala:98)
          at sbt.ErrorHandling$.wideConvert(ErrorHandling.scala:17)
          at sbt.MainLoop$.next(MainLoop.scala:98)
          at sbt.MainLoop$.run(MainLoop.scala:91)
          at sbt.MainLoop$$anonfun$runWithNewLog$1.apply(MainLoop.scala:70)
          at sbt.MainLoop$$anonfun$runWithNewLog$1.apply(MainLoop.scala:65)
          at sbt.Using.apply(Using.scala:24)
          at sbt.MainLoop$.runWithNewLog(MainLoop.scala:65)
          at sbt.MainLoop$.runAndClearLast(MainLoop.scala:48)
          at sbt.MainLoop$.runLoggedLoop(MainLoop.scala:32)
          at sbt.MainLoop$.runLogged(MainLoop.scala:24)
          at sbt.StandardMain$.runManaged(Main.scala:53)
          at sbt.xMain.run(Main.scala:28)
          at xsbt.boot.Launch$$anonfun$run$1.apply(Launch.scala:109)
          at xsbt.boot.Launch$.withContextLoader(Launch.scala:128)
          at xsbt.boot.Launch$.run(Launch.scala:109)
          at xsbt.boot.Launch$$anonfun$apply$1.apply(Launch.scala:35)
          at xsbt.boot.Launch$.launch(Launch.scala:117)
          at xsbt.boot.Launch$.apply(Launch.scala:18)
          at xsbt.boot.Boot$.runImpl(Boot.scala:41)
          at xsbt.boot.Boot$.main(Boot.scala:17)
          at xsbt.boot.Boot.main(Boot.scala)
  [error] java.lang.UnsupportedClassVersionError: com/typesafe/config/ConfigException : Unsupported major.minor version 52.0
  </code></pre>