rerun 04 with matplotlib inline, higher dpi, save results

I don't know what I changed in those slides and should really use a different format...

also rename notebooks with semantic names

rename slides with semantic names

upload hw4 notebook after class

homework 4 solution

minor fixes to hw4 solutions

rerun

upload some solutions to hw3 and hw4

25 update slides, notebooks, push pdf

rix date in 25 slides

start on 25

rename pdf for 18

update 24

rename notebook for 23 because it coveres 24, too