onChangeTab (index) {
      if (!this.isControlled) {
        this.selectedIndex = index
      }

      if (this.isControlled && this.isManual) {
        this.selectedIndex = index
      }

      if (!this.isManual) {
        this.$emit('change', index)
      }
    }
Handles tab chage
@param {Number} index Index to vbe set