Rename default config to always come first

If a custom config file is added that starts with a number or A-C, it will be the first server defined in Nginx. That means the ip address by itself will not point to the default server, but rather whatever server is defined first.
Revert "Rename default config to always come first"

This reverts commit 7af430d5bb368fc0d55705483c147d22aec09162.
Use the default_server designation
Merge pull request #123 from johnpbloch/default-site-config

Rename default config to always come first