Update firstapp.md
Update firstapp.md

简单修饰
Update firstapp.md
Update firstapp.md
Update firstapp.md

整章翻好
Update devtools.md
Update devtools.md
Update firstapp.md
Update firstapp.md

change 【##总结】 --> 【## 总结】
Update devtools.md
Merge pull request #8 from lucyking/master

firstapp和devtools两章
Merge pull request #6 from MozillaChina/master

上游合并
合并修改
Merge branch 'yuanwowo-master'
Merge pull request #16 from yuanwowo/master

Update devtools.md
distribution.md and marketplace.md translation from English to Chinese