added gender-based analysis

also plot and trace gathering refactoring work. binned age group next,
and then possibly binned pre-test score
WIP refactored plots
greatly improved bayesian regression plotting

code now allows for multiple features and heir vs individual
also general plot formatting improvements and refactoring thoughout
WIP running for different groups
full run through
added option for quadratic fit

and updated notebook render
WIP improvements to colour scatterpoints by school
completed MCMC sampling and plotting for all

notebook is in completed state, also written slightly modified df to
sql to allow us to slice/dice dataset outside of the notebook
updated the rendered notebooks with latest
calculated intercept at mean x

added marker, text display on plot and improved the 1:1 (45deg) line
run for all groups etc

these are the most over-complicated plots I’ve ever made, I love it
improved plots, run again, added latest render
update for group wrat

transformed group_wrat to araw