Fixes wrong value returned when getting the vendor dir through Plugin…

…Config

When using `\MagentoHackathon\Composer\Magento\ProjectConfig::getVendorDir()`, the passed array didn't contain the "vendor-dir" key, so the default value was always returned, irrelevant of the configuration in "composer.json".

Also, the said method must always return the absolute path to the vendor folder, as it's the case with Composer.

src/MagentoHackathon/Composer/Magento/ProjectConfig.php

@@ -437,7 +437,11 @@ public function getComposerRepositories()
      */
     public function getVendorDir()
     {
-        return $this->fetchVarFromConfigArray($this->composerConfig, 'vendor-dir', 'vendor');
+        return $this->fetchVarFromConfigArray(
+            $this->composerConfig['config'],
+            'vendor-dir',
+            getcwd() . '/vendor'
+        );
     }
 
     /**

tests/MagentoHackathon/Composer/Magento/ModuleManagerTest.php

@@ -30,7 +30,7 @@ public function setUp()
             new InstalledPackageDumper()
         );
 
-        $config = new ProjectConfig(array(), array('vendor-dir' => 'vendor'));
+        $config = new ProjectConfig(array(), array('config' => array('vendor-dir' => 'vendor')));
         $this->unInstallStrategy =
             $this->getMock('MagentoHackathon\Composer\Magento\UnInstallStrategy\UnInstallStrategyInterface');