minor #283 Use Symfony's helper to format the memory values (javiereguiluz)

This PR was merged into the 1.0-dev branch.

Discussion
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Use Symfony's helper to format the memory values

Less code to maintain for us and the output is almost the same:

### Before

![before](https://cloud.githubusercontent.com/assets/73419/19228575/e50633b2-8ec6-11e6-97c6-1615528aef7e.gif)

### After

![after](https://cloud.githubusercontent.com/assets/73419/19228577/e8476f8c-8ec6-11e6-89bc-7a00274ffc43.gif)

---

Thanks to @mickaelandrieu who tweeted about this helper method and allowed me to learn about it!

Commits
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c3f8200 Use Symfony's helper to format the memory values

Author: javiereguiluz

src/Symfony/Installer/DownloadCommand.php

@@ -21,6 +21,7 @@
 use GuzzleHttp\Event\ProgressEvent;
 use GuzzleHttp\Utils;
 use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Helper\Helper;
 use Symfony\Component\Console\Helper\ProgressBar;
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
@@ -146,10 +147,10 @@ protected function download()
 
             if (null === $progressBar) {
                 ProgressBar::setPlaceholderFormatterDefinition('max', function (ProgressBar $bar) {
-                    return $this->formatSize($bar->getMaxSteps());
+                    return Helper::formatMemory($bar->getMaxSteps());
                 });
                 ProgressBar::setPlaceholderFormatterDefinition('current', function (ProgressBar $bar) {
-                    return str_pad($this->formatSize($bar->getProgress()), 11, ' ', STR_PAD_LEFT);
+                    return str_pad(Helper::formatMemory($bar->getProgress()), 11, ' ', STR_PAD_LEFT);
                 });
 
                 $progressBar = new ProgressBar($this->output, $downloadSize);
@@ -449,26 +450,6 @@ protected function checkPermissions()
         return $this;
     }
 
-    /**
-     * Utility method to show the number of bytes in a readable format.
-     *
-     * @param int $bytes The number of bytes to format
-     *
-     * @return string The human readable string of bytes (e.g. 4.32MB)
-     */
-    protected function formatSize($bytes)
-    {
-        $units = array('B', 'KB', 'MB', 'GB', 'TB');
-
-        $bytes = max($bytes, 0);
-        $pow = $bytes ? floor(log($bytes, 1024)) : 0;
-        $pow = min($pow, count($units) - 1);
-
-        $bytes /= pow(1024, $pow);
-
-        return number_format($bytes, 2).' '.$units[$pow];
-    }
-
     /**
      * Formats the error message contained in the given Requirement item
      * using the optional line length provided.