Improved the DBAL check dependency

The check only accesses the method of the ConnectionRegistry interface, so it does not need to depend on the bigger ManagerRegistry interface
Added file validation checks from ZendDiagnostics
Dumped default config into the readme
Merge pull request #65 from stof/patch-1

Improved the DBAL check dependency
Changed min-dep of ZendDiagnostics to >=1.0.1
Added tests for ZendDiagnostics checks
Fixed composer version requirement for ZendDiagnostics
Merge pull request #66 from frne/zend_file_checks_integration

ZendDiagnostics file checks integration
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