Obey the PIPELINE setting

If pipeline is deactivated (settings.PIPELINE is False) developer
does not want minifyed html.

pipeline/middleware.py

+from django.core.exceptions import MiddlewareNotUsed
 from django.utils.encoding import DjangoUnicodeDecodeError
 from django.utils.html import strip_spaces_between_tags as minify_html
 
+from pipeline.conf import settings
+
 
 class MinifyHTMLMiddleware(object):
+    def __init__(self):
+        if not settings.PIPELINE:
+            # Obey the PIPELINE setting
+            raise MiddlewareNotUsed
+
     def process_response(self, request, response):
         if response.has_header('Content-Type') and 'text/html' in response['Content-Type']:
             try: