Small corrections in the tutorials (#145)

Changes have been made in three different chapters:
- Part 1: Include installation of `jupyterlab` package to allow running
the Lab
- Part 2/Chapter 3: Remove outdated comment about the parameters of `wg`
having to be a single variable
- Part 2/Chapter 4: Update the variable and step type to match the newly
created type of step

book/part1_chapter5.ipynb

@@ -36,6 +36,7 @@
     "python3 -m venv .env # create virtual environment\n",
     "source .env/bin/activate # activate virtual environment\n",
     "pip install -r requirements.txt # install required python dependencies from requirements.txt\n",
+    "pip install jupyterlab # install required package to run the Jupyter Lab\n",
     "maturin develop # build the project with rust bindings\n",
     "```\n",
     "\n",

book/part2_chapter2.ipynb

@@ -159,8 +159,6 @@
     "\n",
     "We didn't pass in witness values for \"c\", because they are calculated in `FiboStep` `wg`.\n",
     "\n",
-    "Note that we need to pass in witness value assignments in a single argument `args` and therefore we use a tuple in this case. `args` can really be any data type as long as it's one single argument.\n",
-    "\n",
     "After creating the first `FiboStep` instance, we loop over `FiboStep` instantiation for 3 more times, each time calculating and passing in a different tuple of assignments. Voila, here's our Fibonacci circuit with 4 `FiboStep` instances:"
    ]
   },

book/part2_chapter4.ipynb

@@ -43,7 +43,7 @@
     "class Fibonacci(Circuit):\n",
     "    def setup(self):\n",
     "        # ...\n",
-    "        self.fibo_step = self.step_type(FiboStep(self, \"fibo_step\"))\n",
+    "        self.fibo_first_step = self.step_type(FiboFirstStep(self, \"fibo_first_step\"))\n",
     "        self.pragma_first_step(self.fibo_first_step)\n",
     "        \n",
     "    def trace(self, args):\n",