perf:use pyyaml to parse hexo meta and perf some vars

[vimiix]

Hi，

Thanks for your nice work, I have changed my blog engine to it. And in this PR, I did some little effort to make it more lovely, as follow:

• use pyyaml lib to parse hexo meta info (it will more stable I think)
• update some template vars in nginx.conf
• add my blog showcase to README

I hope what I did is helpful.

[dongweiming]

Thanks~