Updated some MD and code review recommendations

Author: kschroeder

setup/src/Magento/Setup/Module/Di/Code/Reader/ClassesScanner.php

@@ -39,6 +39,12 @@ public function __construct(array $excludePatterns = [], $generationDirectory =
         $this->generationDirectory = $generationDirectory;
     }
 
+    /**
+     * Retrieves the fully qualified path for var/generation.
+     *
+     * @return string
+     */
+
     public function getGenerationDirectory()
     {
         if ($this->generationDirectory === null) {

setup/src/Magento/Setup/Module/Di/Code/Reader/FileClassScanner.php

@@ -66,6 +66,9 @@ public function getFileContents()
      * Extracts the fully qualified class name from a file.  It only searches for the first match and stops looking
      * as soon as it enters the class definition itself.
      *
+     * Warnings are suppressed for this method due to a micro-optimization that only really shows up when this logic
+     * is called several millions of times, which can happen quite easily with even moderately sized codebases.
+     *
      * @SuppressWarnings(PHPMD.CyclomaticComplexity)
      * @SuppressWarnings(PHPMD.NPathComplexity)
      * @return array