Add AuthenticationServiceInterface
Add docblock description to authenticate()
Add interface docblock
Test
Fix
Fix for PSR-2 standard
Proper use of empty() for PHP < 5.5
Enhance testing that parameter is correct
Merge pull request #5901 from danizord/feature/authentication-service-interface

Add AuthenticationServiceInterface
[#5901] Added note to README
Merge branch 'feature/5901' into develop

Close #5901
Merge pull request #5936 from god107/zf4267

Fix for issue #4267
Merge branch 'hotfix/5936' into develop

Close #5936
Fixes #4267