Escape html text in inspect replies by default

Otherwise, the default docstring <no docstring> was not displayed in html because it was acting as an html tag.

IPython/core/oinspect.py

@@ -16,6 +16,7 b" __all__ = ['Inspector','InspectColors']"
 import ast
 import inspect
 from inspect import signature
+import html
 import linecache
 import warnings
 import os
@@ -531,7 +532,7 b' class Inspector(Colorable):'
         """
         defaults = {
             'text/plain': text,
-            'text/html': '<pre>' + text + '</pre>'
+            'text/html': '<pre>' + html.escape(text) + '</pre>'
         }
 
         if formatter is None: