Fix the title to show nicely in sphinx

Author: gnecula

docs/notebooks/How_JAX_primitives_work.ipynb

@@ -21,9 +21,9 @@
         "colab_type": "text"
       },
       "source": [
-        "# JAX primitives\n",
+        "# How JAX primitives work\n",
         "\n",
-        "*necula@google.com*, September 2019.\n",
+        "*necula@google.com*, October 2019.\n",
         "\n",
         "JAX implements certain transformations of Python functions, e.g., `jit`, `grad`,\n",
         "`vmap`, or `pmap`. The Python functions to be transformed must be JAX-traceable, \n",