add link to the default options

[waldyrious]

I was having a hard time finding this in the docs. Adding the link so it's more discoverable.

[jugglinmike]

Actually, that file is just an example--it has no effect on JSHint's behavior. While it might match the current default behavior, there's no guarantee that it will continue to do so.

This is why the "options" documentation segments the options by the categories "enforcing" and "relaxing". Notice how all the "relaxing" options are about suppressing warnings--these are the constraints that JSHint imposes by default.

[waldyrious]

Since the change in the is PR is not technically correct, I will close it, and continue discussion in #20