Fix MatplotlibDeprecationWarning

MatplotlibDeprecationWarning: Passing non-integers as three-element position specification is deprecated since 3.3 and will be removed two minor releases later.

Author: thomasaarholt

Diff for: Chapter1_Introduction/Ch1_Introduction_PyMC3.ipynb

@@ -209,7 +209,7 @@
     "\n",
     "# For the already prepared, I'm using Binomial's conj. prior.\n",
     "for k, N in enumerate(n_trials):\n",
-    "    sx = plt.subplot(len(n_trials)/2, 2, k+1)\n",
+    "    sx = plt.subplot(len(n_trials)//2, 2, k+1)\n",
     "    plt.xlabel(\"$p$, probability of heads\") \\\n",
     "        if k in [0, len(n_trials)-1] else None\n",
     "    plt.setp(sx.get_yticklabels(), visible=False)\n",