fix supervisor crash by handling case when st_nlink == 0
Add anonymous user test

Creates a grain with a logged in user, and then tests that the a
non-logged in user can access that grain and see its contents as
expected.
Merge pull request #177 from jparyani/add-anonymous-user-test

Add anonymous user test
Merge pull request #168 from dwrensha/lstat

fix supervisor crash by handling case when st_nlink == 0