[L2-1] Minor changes

* Change sentence about `rcParams` dictionary to set style of figures.
* Add code comment about array slicing.

lessons/02_spacetime/02_01_1DConvection.ipynb

@@ -231,7 +231,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Alright. Let's get a little Python on the road. First: we need to load our array and plotting libraries, as usual. And if you noticed in the [*Bonus!* notebook for Module 1](https://nbviewer.jupyter.org/github/numerical-mooc/numerical-mooc/blob/master/lessons/01_phugoid/01_04_Second_Order_Methods.ipynb), we taught you a neat trick to set some global plotting parameters with the `rcParams` module. We like to do that."
+    "Alright. Let's get a little Python on the road. First: we need to load our array and plotting libraries, as usual."
    ]
   },
   {
@@ -245,6 +245,13 @@
     "%matplotlib inline"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "We also set notebook-wide plotting parameters for the font family and the font size by modifying entries of the `rcParams` dictionary."
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 2,
@@ -666,6 +673,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
+    "# Compute the solution using Euler's method and array slicing.\n",
     "u = u0.copy()\n",
     "for n in range(1, nt):\n",
     "    u[1:] = u[1:] - dt / dx * u[1:] * (u[1:] - u[:-1])"