Fix for malformed HTML in notebook 4

Author: Chris Fonnesbeck

4. Statistical Data Modeling.ipynb

@@ -118,6 +118,7 @@
       "\n",
       "<div style=\"font-size: 150%;\">  \n",
       "$$Pr(X=x)=\\frac{e^{-\\lambda}\\lambda^x}{x!}$$\n",
+      "</div>\n",
       "\n",
       "* $X=\\{0,1,2,\\ldots\\}$\n",
       "* $\\lambda > 0$\n",
@@ -152,6 +153,7 @@
       "\n",
       "<div style=\"font-size: 150%;\">  \n",
       "$$f(x) = \\frac{1}{\\sqrt{2\\pi\\sigma^2}}\\exp\\left[-\\frac{(x-\\mu)^2}{2\\sigma^2}\\right]$$\n",
+      "</div>\n",
       "\n",
       "* $X \\in \\mathbf{R}$\n",
       "* $\\mu \\in \\mathbf{R}$\n",