[config/dx] bundle a default fs (and http?) service if none is provided (#179)

bonobo/nodes/basics.py

@@ -4,11 +4,12 @@ import itertools
 from bonobo import settings
 from bonobo.config import Configurable, Option
 from bonobo.config.processors import ContextProcessor
-from bonobo.constants import NOT_MODIFIED
 from bonobo.structs.bags import Bag
 from bonobo.util.objects import ValueHolder
 from bonobo.util.term import CLEAR_EOL
 
+from bonobo.constants import NOT_MODIFIED
+
 __all__ = [
     'Limit',
     'PrettyPrinter',