Something really need to be clarified (ziishaned#48)

* Something really need to be clarified

the `+` is tricky

* add explanation on the optional ?

Thanks for the great project , hope this can help to clarify a bit in Chinese

* Change a bit on .

some typo corrected

Author: AndyZhuang

README-cn.md

@@ -261,7 +261,7 @@
 
 反斜线 `\` 在表达式中用于转码紧跟其后的字符. 用于指定 `{ } [ ] / \ + * . $ ^ | ?` 这些特殊字符. 如果想要匹配这些特殊字符则要在其前面加上反斜线 `\`.
 
-例如 `.` 是用来匹配除换行符外的所有字符的. 如果想要匹配句子中的 `.` 则要写成 `\.`.
+例如 `.` 是用来匹配除换行符外的所有字符的. 如果想要匹配句子中的 `.` 则要写成 `\.` 以下这个例子 `\.?`是选择性匹配`.`
 
 <pre>
 "(f|c|m)at\.?" => The <a href="#learn-regex"><strong>fat</strong></a> <a href="#learn-regex"><strong>cat</strong></a> sat on the <a href="#learn-regex"><strong>mat.</strong></a>

README.md

@@ -176,7 +176,7 @@ zero or more spaces.
 ### 2.3.2 The Plus
 
 The symbol `+` matches one or more repetitions of the preceding character. For example, the regular expression `c.+t` means: lowercase
-letter `c`, followed by at least one character, followed by the lowercase character `t`.
+letter `c`, followed by at least one character, followed by the lowercase character `t`. It needs to be clarified that `t` is the last `t` in the sentence.
 
 <pre>
 "c.+t" => The fat <a href="#learn-regex"><strong>cat sat on the mat</strong></a>.