Include example config to help devs setup app on new environments

Thought you might like a little extra practice at reviewing and merging pull requests into master.

If we need to setup this app on any other new environments as I did earlier then having this `application.example.yml` file will be helpful to reference. 

The `application.example.yml` ignore has been removed from `.gitignore`, but the `application.yml` line has been left in as we want to continue to protect that file as it's the one with the sensitive information in it.

If you're happy with the changes go ahead and merge this branch into master.