Reverts changed in condition for #1066

Thanks to @boenrobot's comments I have reverted the change to the date
detection method and added a comment why this construct was necessary.
Merge branch 'develop' of github.com:phpDocumentor/phpDocumentor2 into develop
Refactor LegacyNamespaceConverter plugin

The LegacyNamespaceConverter was recently contributed by @david0. To
match the Coding Standards I have updated the plugin with DocBlocks and
code formatting changes.