Little girl Cytosine catches something wrong in 2.md

[Lovegood]

The following items lacks a direction of needing a SPACE behind Markdown keywords.

1. line 72
2. line 136
3. line 160

A typo

1. line 182:"死个空格"should be turned into "四个空格"
   This little error also is submitted in this issue2.md内错字 #1

A optional addition item

1. line 218:上面五种方式中，前四种加不加空行都好使，最后一种不加空行不好使>w<

Last but not least, thank you very much for your selfless devotion in this tutorial,Cytosine wants to give you ten thousand little flowers>w<
That's all.>///<