Pad interact widgets.

IPython/html/static/widgets/less/widgets.less

@@ -1,6 +1,13 @@
 @widget-width: 350px;
 @widget-width-short: 150px;
 
+// Pad interact widgets by default.
+.widget-interact {
+    div, input {
+        padding: 2.5px;
+    }
+}
+
 .widget-area {
     /*
     LESS file that styles IPython notebook widgets and the area they sit in.

IPython/html/widgets/interaction.py

@@ -181,7 +181,7 @@ def interactive(__interact_f, **kwargs):
     co = kwargs.pop('clear_output', True)
     manual = kwargs.pop('__manual', False)
     kwargs_widgets = []
-    container = Box()
+    container = Box(_dom_classes=['widget-interact'])
     container.result = None
     container.args = []
     container.kwargs = dict()