Add a place where people can load other config files.

Give a commented out example of how to load override config files,
hopefully this will show people that they can load other config files as
well.
Merge pull request #1602 from markstory/3.0-config-local

3.0 - local config
Shuffle files around for the impending repo split.
Remove skel directory.

Project bake will be using composer in the future. There is no need to
have a skeleton directory in that world.
First pass at making ProjectTask wrap and proxy to composer.

Instead of using the skel dir that no longer exists, composer should be
used instead.