Update AnnotationsBag.php

Added method to merge attributes
Merge branch 'desenv' of https://github.com/beneditocarlos/annotations into merge
improving tests for AnnotationsBag::merge @benecarlos
removing old tests from when AnnotationsBag had no ParserRules to validate keys

closes #12
allowing chainning in AnnotationsBag::merge + updated tests + updated docb
(re)activating "lost" test from super @nyamsprod