更正错别字(Correct the wrong character)

解释如下：
“界面”就是实实在在看到的，独立的。并且，使用“界面”更符合简体中文的习惯。
界面和介面的区分如下：
http://www.zhihu.com/question/19905127
http://wenwen.soso.com/z/q202320185.htm
Merge pull request #3 from diguage/patch-1

更正错别字，优化措辞(Correct the wrong character)
Update starting quote
Fix validation inconsistency (fixes #67)
Fix "Rails 3 Way" url (fixes #60)
Merge branch 'master' of https://github.com/bbatsov/rails-style-guide
fix “Rails 3 way” url