Fixing README and adding a system.exit on injector failure from 0.6.x branch

 Kill process if Guice fails to create Injector

    Right now, createInjector() can create threads that live beyond the
    parent/main thread. When an exception occurs inside createInjector,
the
    main thread dies, but the process continues - this is bad, if the
    service can’t start correctly it should exit, not continue running
    other threads without handling requests.

    Thanks @snappieT