1.0.0-beta9

• made compatible with Symfony 3.0
• added JSON schema for path mapping files: path-mappings-schema-1.0.json
• upgraded to webmozart/glob 4.1 to improve performance
• renamed Resource to PuliResource
• renamed AbstractPathMappingRepository to AbstractJsonRepository
• renamed PathMappingRepository to JsonRepository
• renamed OptimizedPathMappingRepository to OptimizedJsonRepository
• changed constructor arguments of JSON repositories from KeyValueStore
  to paths of JSON files
• added AbstractEditableRepository
• added ChangeStream
• added VersionList
• added NoVersionFoundException
• added InMemoryChangeStream
• added KeyValueStoreChangeStream
• added JsonChangeStream
• added PuliResource::getVersions()
• added ResourceRepository::getVersions()
• added LinkResource::getTarget()
• made LinkResource serializable