Fixes #196

Return InvalidAppMaster if Class.forName fails. This message will be stored in the AppManager.appMasterRegistry and returned to the client when the client issues a ShutdownApplication(appId) so the client knows why the appmaster failed. Note we need to account for some sort of history server so an audit log exists similar to YARN's history manager and tracks all appmasters execution. This will be addressed is a subsequent issue opened.
Also upgraded akka to 2.3.8 which removes some bogus disassociated messages.

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I think you make a reasonable argument. One could say that having the appmaster start is part of the application submit process. It also may be better to change the examples so that they get appmaster details instead of sleeping, this would be more in line with typical YARN apps. This would argue for storing this type of information in a new map within the AppManager. I will refactor to address these issues, because of refactoring which will be more extensive, this fix will likely also address #208, #221. Thanks.