v1.0.4

• Added Optimizer::valid_compression_level for checking if the compression level is valid
• Added Response::getResultByFileName for getting optimization Result instance by file name
• Force the success property of the Result class to be always int
• Added two helper methods isSuccessfullyOptimized() and isAlreadyOptimized() to the Result class
• Added saveAsFile() and getSavedBytes() to the ResultWebP class