Added an option to display 95% CIs on skill  and other metrics in plot_skills_bins.py
Variable under USER DATA is confidence_interval_flag = True
This also required a change in the summarize method to calculate std (so 95%CI +- 2*std)

Also incremental progress on the mansucript.
IMPORTANT! changed plot_skills_bins.py --> plot_skillz_sets.py to be more consistent with the text.
Plane is about to land! Changed section structure a bit in the manuscript.