assign支持promise, fix #139
assign支持promise, fix #139

75team/thinkjs,Qihoo360/thinkjs,maxzhang/thinkjs,maxzhang/thinkjs,snadn/thinkjs,75team/thinkjs,thinkjs/thinkjs,akira-cn/thinkjs,maxzhang/thinkjs,74sharlock/thinkjs,75team/thinkjs,lukw00/thinkjs,74sharlock/thinkjs,akira-cn/thinkjs,lukw00/thinkjs,akira-cn/thinkjs