Add note about --auth being enabled for MongoDB

Now that MongoDB is started with `--auth` by default it makes sense to let people know that they can can advantage of this by adding users to the admin database if they want to test authentication.
add language: go to the go docs
Merge pull request #306 from TylerBrock/patch-1

Add note about --auth being enabled for MongoDB
Merge branch 'master' into rubygems_doc
Renamed blog post