Switch driver to pg. [#3635 state:resolved]

railties/lib/rails/generators/rails/app/templates/config/databases/postgresql.yml

 # PostgreSQL. Versions 7.4 and 8.x are supported.
 #
-# Install the ruby-postgres driver:
-#   gem install ruby-postgres
-# On Mac OS X:
-#   gem install ruby-postgres -- --include=/usr/local/pgsql
+# Install the pg driver:
+#   gem install pg
+# On Mac OS X with macports:
+#   gem install pg -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config
 # On Windows:
-#   gem install ruby-postgres
+#   gem install pg
 #       Choose the win32 build.
 #       Install PostgreSQL and put its /bin directory on your path.
 development: