Minor errors in the 2nd part of our transport tutorial

[glatterf42]

While working on iiasa/ixmp4#108, I noticed a few minor error with the second part of our existing transport tutorial. It's probably not urgent to fix them since we are already re-implementing them in ixmp4.

ixmp/tutorial/transport/py_transport_scenario.ipynb

Lines 200 to 201 in e12922f

	"scen_detroit.add_par('d', ['seattle', 'detroit'], 1.7, 'cases')\n",
	"scen_detroit.add_par('d', ['san-diego', 'detroit'], 1.9, 'cases')"

The units here need to be "km", not "cases".

ixmp/tutorial/transport/py_transport_scenario.ipynb

Line 18 in e12922f

"0. Launch an ixmp.Platform instance and retrieve the ixmp.Scenario instance of Dantzig's transport problem\n",

There needs to be a newline before this one to render the list properly.