Merge pull request #176 from stanzhai/develop

【校对】人工逐节校对中，完善文档格式，代码风格，明显错误检查
merge 2.21,2.23,3.5 confilicts
merge 2.21,3.5 confilicts
correct 2.21 code mistakes
correct 2.21 code mistakes
fix 3.6 attributes
fix 3.7 patterns
fix 3.8 generic parameters and arguments
fix 3.10 statements
Merge branch 'develop' of https://github.com/stanzhai/the-swift-programming-language-in-chinese into develop