Patched Hydra::PolicyAwareAccessControlsEnforcement to properly handle a...

Patched Hydra::PolicyAwareAccessControlsEnforcement to properly handle anonymous users (i.e., current_user is nil)

by amending #policies_with_access (previously returned empty list when current_user is nil)
and #apply_policy_individual_permissions.

Added test policies for public read and discover access.

Fixes #39.