add draft translation for section 2.1
translate map, fold and filter of chapter 02
fix merge
capitalize TOC of section 2.1, 2.2
update translation of high order function of chapter 02
Merge pull request #1 from jcouyang/en-version

update revised chapter 01 from jcouyang's repo
update README of chapter 02, the higher-order function
translate more on README.md of chapter 02
translate currying of chapter 02
revise chapter 1 :uk:
revise :uk: 2.1 2.2
merge and revise