Fix exclude files via config (#54)

* Update test coverage file path and clean up .gitignore
* Fix exclusion pattern merging in source file scanning

Author: floriankraemer

.gitignore

@@ -13,4 +13,3 @@
 infection.log
 phive.phar
 phpcca.phar
-/*.xml

src/Business/Cognitive/CognitiveMetricsCollector.php

@@ -200,7 +200,10 @@ private function isExcluded(string $classAndMethod): bool
      */
     private function findSourceFiles(string $path, array $exclude = []): iterable
     {
-        return $this->directoryScanner->scan([$path], ['^(?!.*\.php$).+'] + $exclude);
+        return $this->directoryScanner->scan(
+            [$path],
+            array_merge(['^(?!.*\.php$).+'], $exclude)
+        );
     }
 
     /**