Added code to produce plot of calibration curve, calibration score code stub

[spencermyoung513]

This MR was mostly for me to check my understanding of how calibration curves get drawn for regression models, but I figured it would be useful to have a function in the repo for future experiments. I'd love a check to make sure I'm understanding/creating these correctly

[porterjenkins]

Yeah this is exactly right for Gaussian data. You should be able to generalize this to any probability distribution over the output.