Added visibility
Accept nested attributes for permissions
Merge pull request #93 from projecthydra/visibility_and_permissions

Added visibility
Remove PSU as a permission value
Adds #asset_param_key method to DownloadBehavior to support overriding the default params key (:id) for the asset PID.
Test added for overriding #asset_param_key in DownloadController.
Substituted double for the now deprecated mock() and stub()
Merge pull request #95 from projecthydra/remove_psu

Remove PSU as a permission value
Merge pull request #96 from dchandekstark/download-behavior-asset-param-key

Adds #asset_param_key method to DownloadBehavior
Remove lib/hydra.rb so that the hydra gem can load normally
without ```require: 'hydra6'``` in the Gemfile
Merge pull request #97 from projecthydra/use_double

Substituted double for the now deprecated mock() and stub()
Merge pull request #98 from projecthydra/remove_hydra

Remove lib/hydra.rb so that the hydra gem can load normally
Preparing for 6.4.0.pre1 release
Merge pull request #99 from projecthydra/nested_permissions

Accept nested attributes for permissions
Preparing for 6.4.0.pre2 release
Remove duplicate code
Merge pull request #100 from projecthydra/remove_duplicate_code

Remove duplicate code
Preparing for 6.4.0.rc1 release
Deprecate Hydra::ModelMixins::CommonMetadata
Deprecate Hydra::ModelMixins::SolrDocumentExtension
Hydra::PolicyAwareAbility#policy_pid_for modified to handle multiple objects having different policies (Fixes #101).
Implemented pending tests for Hydra::PolicyAwareAbility#test_read_from_policy and #test_read_from_policy.