Code/docs for second round of Wallac testing

Tested the Wallac after the dispenser was repaired.
Switched over to using fit function in new bax_heat module

First step in centralizing the code for doing the bax_heat fits.
Docs for bax_heat_auto_titration, with two_exp fits

Includes new code for running two_exp fits on stochastic simulation
results, and fitting to data.
Rewrote reporters.bax_heat to use code in plots.bax_heat
Translocation titration comparison