[README] Update status badge to point to CircleCI.
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xxclouddd/eigen,ichu501/eigen,srrvnn/eigen,Shawn-WangDapeng/eigen,gaurav1981/eigen,liduanw/eigen,ashkan18/eigen,ppamorim/eigen,1aurabrown/eigen,foxsofter/eigen,artsy/eigen,ACChe/eigen,orta/eigen,ACChe/eigen,ashkan18/eigen,liduanw/eigen,srrvnn/eigen,foxsofter/eigen,neonichu/eigen,ashkan18/eigen,ichu501/eigen,ayunav/eigen,srrvnn/eigen,TribeMedia/eigen,srrvnn/eigen,artsy/eigen,orta/eigen,foxsofter/eigen,Shawn-WangDapeng/eigen,ashkan18/eigen,ppamorim/eigen,mbogh/eigen,TribeMedia/eigen,ppamorim/eigen,1aurabrown/eigen,neonichu/eigen,liduanw/eigen,liduanw/eigen,mbogh/eigen,TribeMedia/eigen,mbogh/eigen,ayunav/eigen,Havi4/eigen,TribeMedia/eigen,Shawn-WangDapeng/eigen,gaurav1981/eigen,neonichu/eigen,neonichu/eigen,ACChe/eigen,ichu501/eigen,xxclouddd/eigen,Shawn-WangDapeng/eigen,Havi4/eigen,artsy/eigen,zhuzhengwei/eigen,TribeMedia/eigen,foxsofter/eigen,ayunav/eigen,xxclouddd/eigen,zhuzhengwei/eigen,ACChe/eigen,ashkan18/eigen,artsy/eigen,ichu501/eigen,ACChe/eigen,neonichu/eigen,artsy/eigen,gaurav1981/eigen,zhuzhengwei/eigen,1aurabrown/eigen,ichu501/eigen,artsy/eigen,1aurabrown/eigen,Havi4/eigen,ayunav/eigen,artsy/eigen,srrvnn/eigen,ayunav/eigen,ppamorim/eigen,gaurav1981/eigen,foxsofter/eigen,orta/eigen,zhuzhengwei/eigen,liduanw/eigen,orta/eigen,xxclouddd/eigen,Havi4/eigen,gaurav1981/eigen,Shawn-WangDapeng/eigen,xxclouddd/eigen,mbogh/eigen