Fixing concat, it breaks some files if there is no new line.

When concatenating JS files that are NOT minified for development purpose for example that contain comments /*..*/ it will cause syntax errors in the concatenated file.

src/Task/File/Concat.php

@@ -73,7 +73,7 @@ public function run()
                     return Result::error($this, sprintf('File %s not found', $file));
                 }
 
-                $dump .= file_get_contents($file);
+                $dump .= file_get_contents($file) . "\n";
             }
         }