Python 3 print() is a "function"

* responding to @wholmgren comments
* fix pv concepts and python concept header markup to be consistently 3
  hashes for all tutorials (none in tut3 and using 4 hashes in tut4)
* add pop quiz to tut3 on module temperatures

Author: mikofski

Diff for: Tutorial 0 - Overview.ipynb

@@ -162,7 +162,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 1,
    "metadata": {
     "slideshow": {
      "slide_type": "subslide"
@@ -184,7 +184,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 2,
    "metadata": {
     "slideshow": {
      "slide_type": "subslide"
@@ -197,7 +197,7 @@
        "5"
       ]
      },
-     "execution_count": 6,
+     "execution_count": 2,
      "metadata": {},
      "output_type": "execute_result"
     }

Diff for: Tutorial 1 - TMY Weather Data.ipynb

@@ -35,19 +35,19 @@
     }
    },
    "source": [
-    "Steps:\n",
+    "### Steps:\n",
     "- [Weather data in PV performance models](#Weather-Data-&-PV)\n",
     "- Looking at a sample weather data file\n",
     "- Where to get weather data from? \n",
     "- Weather data to API\n",
     "\n",
-    "PV Concepts:\n",
+    "### PV Concepts:\n",
     "- TMY\n",
     "- GHI, DNI, DHI\n",
     "- DryBulb, Wspd\n",
     "- Irradiance vs. Insolation\n",
     "\n",
-    "Python Concepts:\n",
+    "### Python Concepts:\n",
     "- Exploring a Pandas dataframe (`df`): `len()`, `df.head()`, `df.keys()`\n",
     "- [pvlib input-output tools](https://pvlib-python.readthedocs.io/en/stable/api.html#io-tools)\n",
     "- Ploting a Pandas dataframe (`df`): `df.plot()`\n",
@@ -122,7 +122,7 @@
    "source": [
     "#### First Step: Import Libraries\n",
     "\n",
-    "In Python, some commands are builtin like `print()` but others must be imported before they can be used. For this notebook we're going to import three packages:\n",
+    "In Python, some functions are builtin like `print()` but others must be imported before they can be used. For this notebook we're going to import three packages:\n",
     "* [pvlib](https://pvlib-python.readthedocs.io/en/stable/) - library for simulating performance of photovoltaic energy systems. \n",
     "* [pandas](https://pandas.pydata.org/) - analysis tool for timeseries and tabular data\n",
     "* [matplotlib](https://matplotlib.org/) - data visualization for Python\n",

Diff for: Tutorial 2 - POA Irradiance.ipynb

@@ -22,7 +22,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "####  PV Concepts:\n",
+    "###  PV Concepts:\n",
     "\n",
     "- STC Parameters\n",
     "- IV Curve\n",
@@ -37,7 +37,7 @@
     "- Low light and temperature module performance\n",
     "- IEC 61853 standard \n",
     "\n",
-    "#### Python Concepts:\n",
+    "### Python Concepts:\n",
     "\n",
     "- [`numpy.meshgrid`](https://numpy.org/doc/stable/reference/generated/numpy.meshgrid.html)\n",
     "- `try: except` clauses to catch errors\n",

Diff for: Tutorial 3 - Module Temperature.ipynb

@@ -1,4 +1,4 @@
 matplotlib==3.3.4
 numpy==1.19.2
 pandas==1.2.3
-pvlib==0.8.0
+pvlib==0.8.1