Address dollar sign formatting in issue 145 (#159)

* fix dollar sign formatting

* replace with alternates to appease black formatting

Author: bpaul4

idaes_examples/notebooks/docs/unit_models/reactors/stoichiometric_reactor.ipynb

@@ -306,7 +306,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Now, let us add expressions to compute the reactor cooling cost (\\\\$/s) assuming a cost of 2.12E-5 \\\\$/kW, and the heating utility cost (\\\\$/s) assuming 2.2E-4 \\\\$/kW. Note that the heat duty is in units of watt (J/s). The total operating cost will be the sum of the two, expressed in \\\\$/year assuming 8000 operating hours per year (~10\\% downtime, which is fairly common for small scale chemical plants):"
+    "Now, let us add expressions to compute the reactor cooling cost in USD/s assuming a cost of 2.12E-5 USD/kW, and the heating utility cost in USD/s assuming 2.2E-4 USD/kW. Note that the heat duty is in units of watt (J/s). The total operating cost will be the sum of the two, expressed in USD/year assuming 8000 operating hours per year (~10 percent downtime, which is fairly common for small scale chemical plants):"
    ]
   },
   {