Merge pull request #374 from wesleyacheng/fix-chapter3-header

fix missing chapter 3 header

03_classification.ipynb

@@ -871,6 +871,13 @@
     "cross_val_score(sgd_clf, X_train_scaled, y_train, cv=3, scoring=\"accuracy\")"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Error analysis"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 64,