Add errata from the manning site, clarify

Author: elistevens

docs/errata.html

@@ -196,6 +196,14 @@ <h2>Page 258</h2>
         flagged as nodules.
     </p>
 
+    <h2>Page 272</h2>
+    <p>Delete the two text snippets "1((CO10-1))" and "1((CO10-2))" from Listing 10.12.</p>
+<pre>
+    candidate_t,
+    pos_t,
+</pre>
+    <p>The code annotation "This is our training sample." should cover those two lines as well.</p>
+
     <h2>Page 277</h2>
     <p><i>The first code annotation should read:</i></p>
     <p>