Fix code churn typo. Add update from Fernando.

IPythonReviewTime.ipynb

@@ -117,7 +117,7 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "Before we answer the question posed at the beginning of this article, I'll answer some easier questions. First off: which files in IPython have been committed to the most? This is a simplified version of \"code churn\" code churn which is [reasonably](https://research.microsoft.com/apps/pubs/default.aspx?id=69126) [effective](http://google-engtools.blogspot.ca/2011/12/bug-prediction-at-google.html) for predicting bugs. (More complicated models include lines modified or [take semantic differences into account](http://dl.acm.org/citation.cfm?id=1985456)). Since this is Friday night and I'm not trying to get a paper into ICSE, I'll just take the number of commits for each `.py` file."
+      "Before we answer the question posed at the beginning of this article, I'll answer some easier questions. First off: which files in IPython have been committed to the most? This is a simplified version of \"code churn\" which is [reasonably](https://research.microsoft.com/apps/pubs/default.aspx?id=69126) [effective](http://google-engtools.blogspot.ca/2011/12/bug-prediction-at-google.html) for predicting bugs. (More complicated models include lines modified or [take semantic differences into account](http://dl.acm.org/citation.cfm?id=1985456)). Since this is Friday night and I'm not trying to get a paper into ICSE, I'll just take the number of commits for each `.py` file."
      ]
     },
     {
@@ -810,7 +810,7 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "The first thing that stands out is (as of this writing) commit `796a90bdeef3770` has a delta of one minute. Fernando reported 8 minutes, which is much more plausible. This makes me wonder if some people have out-of-date clocks.\n",
+      "The first thing that stands out is (as of this writing) commit `796a90bdeef3770` has a delta of one minute. Fernando reported 8 minutes, which is much more plausible. This makes me wonder if some people have out-of-date clocks. **Update: Fernando says that the review time was 1 minute; 8 minutes was from bug to pull request to commit.**\n",
       "\n",
       "Anyways, let's make a box plot. Box plots are fun."
      ]