Ignore current site config

site.coffee is meant to house configuration for the current site only.
It should not be checked in as part of the app.
Move site-specific config out of environments

The development and production config files no longer have settings that
should be specific to the current site. Those settings will now be in a
site.coffee that can be copied or symlinked into the config directory.
site.coffee.ex is a starting template for this.