update nunjucks to 2.2.0
update nunjucks to 2.2.0

maxzhang/thinkjs,Qihoo360/thinkjs,maxzhang/thinkjs,snadn/thinkjs,akira-cn/thinkjs,maxzhang/thinkjs,akira-cn/thinkjs,75team/thinkjs,75team/thinkjs,akira-cn/thinkjs,thinkjs/thinkjs,75team/thinkjs