CHANGELOG
=========
2.2.0
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* added a `keepKeys()` method for array nodes (to avoid key normalization)
* added numerical type handling for config definitions
* added convenience methods for optional configuration sections to ArrayNodeDefinition
* added a utils class for XML manipulations
2.1.0
* added a way to add documentation on configuration
* implemented `Serializable` on resources
* LoaderResolverInterface is now used instead of LoaderResolver for type
hinting