Change the warning in the jupyter notebook for creating content,

regarding name collisions between method and property names, to
not pick on the Mapping methods specifically.  The problem is
more general than that: stix objects have more methods than those.
Instead of listing them all out, a more general statement is
made, that accessing those attributes will result in a bound
method, not a STIX property value.

docs/guide/creating.ipynb

@@ -334,14 +334,13 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "-----\n",
-    "### Warning\n",
-    "Note that because these objects are designed to be usable as `Mapping`s, the attributes of that interface retain their mapping meanings and can't be used to access STIX object properties.  This includes the attributes:\n",
-    "- keys\n",
-    "- values\n",
-    "- items\n",
-    "- get\n",
-    "-----"
+    "<div class=\"alert alert-warning\">\n",
+    "\n",
+    "**Warning**\n",
+    "\n",
+    "Note that there are several attributes on these objects used for method names.  Accessing those will return a bound method, not the attribute value.\n",
+    "\n",
+    "</div>\n"
    ]
   },
   {