fetch_old_gci_task_data: Fix command

The command had missing imports and incorrectly used
yaml.

Related to coala#3

gci/management/commands/fetch_old_gci_task_data.py

@@ -1,3 +1,5 @@
+import os.path
+
 import requests
 
 from django.core.management.base import BaseCommand
@@ -20,10 +22,10 @@ def handle(self, *args, **options):
         r.raise_for_status()
 
         with open(os.path.join(output_dir, 'tasks.yaml'), 'w') as f:
-            yaml.dump(r.content, f)
+            f.write(r.content)
 
         r = requests.get(deploy_url + '/static/instances.yaml')
         r.raise_for_status()
 
         with open(os.path.join(output_dir, 'instances.yaml'), 'w') as f:
-            yaml.dump(r.content, f)
+            f.write(r.content)