Merge pull request #175 from BluntBlade/master

同步更新
Update index.md
Merge pull request #176 from rwifeng/patch-5

Update index.md
delete line break
Merge pull request #177 from rwifeng/patch-6

delete line break
Update pipeline.md

rm sync video fop
Update style.md

replace vframe example to image fop
Update concepts.md

replace vframe with image fop
Merge pull request #178 from rwifeng/patch-7

Update pipeline.md
Merge pull request #179 from rwifeng/patch-8

Update style.md
Merge pull request #180 from rwifeng/patch-9

Update concepts.md
从 kb.qiniu.com 中移回账号管理文档，并隐藏（仅通过链接访问，没有导航项目）。