:octocat: +several coverage tests & cleanup

src/Decoder/Binarizer.php

@@ -103,7 +103,7 @@ final class Binarizer{
 		// If there is too little contrast in the image to pick a meaningful black point, throw rather
 		// than waste time trying to decode the image, and risk false positives.
 		if($secondPeak - $firstPeak <= $numBuckets / 16){
-			throw new QRCodeDecoderException('no meaningful dark point found');
+			throw new QRCodeDecoderException('no meaningful dark point found'); // @codeCoverageIgnore
 		}
 
 		// Find a valley between them that is low and closer to the white peak.