message: Fix some react warnings in GroupMemberList
  - If the list contains two users twice, react would warn about duplicate keys. Use `index` instead.
  - Check if unmounted before setting state after fetching members.
diff: @@ -59,6 +59,7 @@ export default withMatrixClient(React.createClass({
  },
  _fetchMembers: function() {
  + if (this._unmounted) return;
  this.setState({
  members: this._groupStore.getGroupMembers(),
  invitedMembers: this._groupStore.getGroupInvitedMembers(),
  @@ -105,9 +106,9 @@ export default withMatrixClient(React.createClass({
  });
  }
  - memberList = memberList.map((m) => {
  + memberList = memberList.map((m, index) => {
  return (
  - <GroupMemberTile key={m.userId} groupId={this.props.groupId} member={m} />
  + <GroupMemberTile key={index} groupId={this.props.groupId} member={m} />
  );
  });
  