update reference pages
add blank
fix Chapter 1.2

1 line code missing
missing Class Movie declare
Merge pull request #126 from zac1st1k/gh-pages

1.2 章 遗漏一行代码
“numbers.map({ number in 3 * number })”
Merge pull request #128 from leee1001/gh-pages

2.18 章节 类型检查（Type Casting）遗漏代码补全
add highlight
Update 16_Automatic_Reference_Counting.md

code error
Merge pull request #130 from yulingtianxia/gh-pages

Update 16_Automatic_Reference_Counting.md
Fixed #129
Fixed #127
update ARC

根据第一章的翻译，“显式展开的可选”应该为“隐式解析可选”
Update ARC

根据Initialization那章的翻译，“两步构造函数”应叫做“两段式构造过程”
Merge pull request #131 from yulingtianxia/develop

update ARC
update ARC

1.“显式”应为“隐式”
2.修改一些翻译不恰当的地方
2.6 章节 函数（Functions） 错别字修改
Merge pull request #134 from yulingtianxia/develop

update ARC
update reference pages
merge changes
update ARC, fix some bugs & typing errors