add bqskit <> mitiq tutorial

[natestemen]

Here is the main takeaway from the updated notebook:

Data used for this plot is:

• 200 random circuits (cirq.testing.random_circuit)
• 4 qubits
• depth = 40
• noise only on 2 qubit gates

[natestemen]

Thanks both for the comments! I agree the notebook could use further tweaking. As for now I will follow Nathan's advice and get this merged and sent over to Ed/Costin in time for IEEE quantum week. They might have comments as well that can be factored into further improvements.