Fetching of user's verified keys through standard OAuth scope.

Allow the fetching of a user's verified key list without
requiring to have an OAuth user scope (which implies
user's profile READ/WRITE permissions).
This would relax the requirements of GitHub OAuth scope
when fetching public information such as their SSH
public keys.
Merge pull request #61 from lucamilanesio/master

Fetching of user's verified keys through standard OAuth scope.