Fixed autoloader so it will run tests properly without Composer
Changed InvalidArgumentException to be in local namespace
Added some more tests for standalone configuration object
Micro code cleanup
Fixed possible variables conflict
Renamed namespace for test fixtures
Removed custom InvalidArgumentException class in favor to standard exception of same kind
Added tests for onConfigChange callback method calling
Micro optimization
Minor tests refactoring
Added test for configuration modification using object as modifications source
Fixture classes for standalone config object are refactored to move common functionality into separate base class