Reduce simulation time

Optimization

• Optimize qmix.qtcurrent using Numba and JIT. 4 tone simulations are now 1.5 times faster!
• Add basic timing scripts for qmix.qtcurrent. See speed/ directory.

Changes

• Move the code that is used for analyzing the IF response into a new module: qmix.exp.if_response.

New Features

• Add ability to force embedding impedance in qmix.exp.exp_data.RawData. The embedding voltage will then be calculated using this value.

Testing

• Improve test coverage for qmix.circuit, qmix.respfn, and qmix.exp.exp_data.
• Add tests for new module (qmix.exp.if_response).
• Add notebook to recreate plots from Kittara's thesis. (For the purpose of validation.)

Minor Changes

• Improved progress messages from qmix.harmonic_balance.harmonic_balance.
• Add ability to plot response function (qmix.respfn.RespFn).
• Always use default parameters from qmix.exp.parameters (i.e., reduce the number of magic numbers).
• Add ability to call qmix.respfn.RespFn by adding __call__ method. This will return the interpolated response function (a complex value).
• Fix error in qmix.harmonic_balance.harmonic_balance (when Thevenin voltage is checked).
• Other minor changes to documentation.