Abstraction of email transport and message generation.

This request contains one commit that was merged in from SimianArmy on Netflix:master (removal of java 1.6 requirement).  Tests run (and new tests written), no regressions.  Comments welcome!

The purpose of this PR is to start work on abstraction of "cloud" and "cluster" ideas (all still abstract) from some of the tightly coupled AWS dependencies that exist in those base classes.  This particular branch allows a non-aws user to send notifications through a specified SMTP server.  Our particular use case is that we _are_ a cloud provider (rather than an app developer who deploys _to_ a cloud provider).  SimianArmy has the same intrinsic value for cloud providers (taking out machines to see if the cluster will survive without interrupting the user experience), but we obviously can't route mail through the AWS email service.