Start tracking WordPress trunk as a submodule

This is intended to keep the repository tied to a specific version of WordPress.
Add .gitignore
Fire up the README
Add a content directory

WordPress will be installed in a subdirectory at the same level as our content directory so that we can keep the WordPress repository as clean as possible.
Add files needed at the site root by WordPress

The wp-config and local-config aren't yet setup completely, but close.
Introduce mu-plugins, plugins, and themes directory with blank index.php files
Add TwentyThirteen to the WSUWP Platform as a parent theme option