[ch02ex] bok.csv 추가, bok.txt 발표자 자료로 대체.
[update]

Merge branch 'master' of https://github.com/psygement/ecor

Conflicts:
	part1/ch02ex/casestudy.html
	part1/ch02ex/casestudy.md
	part1/ch02ex/data/bok.txt
	part1/ch02ex/figure/unnamed-chunk-5.png
	part1/ch02ex/figure/unnamed-chunk-7.png