A better way to opt-out

In the absence of a formal way to set our profiles to private for this kind of activity we can (should?) adopt a community standard. I recommend we use a `.optout` repo.

This pull request adds support in **resume** to check a user's repo list for a `.optout` repo. If the repo is present the user is considered `opted_out`. With this change people won't have to fork this project and add their name to a list and we will, potentially, have a solution that works for similar applications/mashups/etc.