add new translation for chapter 2
[vi] Update chapter 2
[vi] First commit of the new year
[vi] Finished chapter 2
[vi] Finished chapter 2
Merge remote-tracking branch 'upstream/master'
[vi] made some changes on chapter 2
[vi] copied chapter 3 for translation
Merge pull request #599 from tuanva/master

[vi] Finished chapter II