Merge pull request jerry-git#6 from vivek28111992/patch-1

Store the return value of str.replace

Author: jerry-git

notebooks/beginner/strings.ipynb

@@ -92,7 +92,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "my_string.replace('a', '?')\n",
+    "my_string = my_string.replace('a', '?')\n",
     "print(my_string)"
    ]
   },