ITC model now works

[harmsm]

Last version worked to fit simulated data; however, this did not work on real data.

• I updated how the calculation is done, properly accounting for heats of dilution and other experimental nuisance parameters. It now works on real data.
• I removed y_calc as a part of the GlobalModel itself. You a now call model to get those values, but this generates a numpy array that is not held onto by the class. (This cleanly separates the model outputs from the model itself).
• The function now assumes that all data comes in with SI units (molar, L, etc.). This will have to be enforced when we bring in the yaml experiment loading framework.
• Bumped versino to 0.2.0 .