Merge pull request #2 from CocoaChina-editors/master

merge to edit
Merge pull request #85 from bytegh/master

Merge pull request #2 from CocoaChina-editors/master
校正2-4和4-1

校正2-4和4-1
Merge branch 'ChildhoodAndyCorrection'
Merge branch 'master' of https://github.com/CocoaChina-editors/Welcome-to-Swift
修改2-1部分格式