finish excercise 5 translate
excercise 6 need to be check the 'export' translate
finish excercise 7 translate
fix some words
finish excercise 8 translate
fininsh some translate
finish all excercise translate
finish help, credits, README.md translate
replace 問題 to 習題
Merge branch 'master' of github.com:billy3321/learnyounode into billy3321-master
Merge branch 'billy3321-master' into tanslation-zh-tw