fix elastic header example in IE
fix elastic header example in IE

fergaldoyle/vue,karevn/vue,galenyuan/vue,Endika/vue,th0r/vue,shupan123/vue-fixed-type,Endika/vue,seedalpha/vue,galenyuan/vue,th0r/vue,seedalpha/vue,shupan123/vue-fixed-type,karevn/vue,diermengdierme/vue,lepture/vue,karevn/vue,th0r/vue,seedalpha/vue,diermengdierme/vue,Endika/vue,shupan123/vue-fixed-type,fergaldoyle/vue,diermengdierme/vue,galenyuan/vue,lepture/vue,lepture/vue,fergaldoyle/vue