message: Make read receipt's titles more explanatory
  Throwing this one in a suggestion while I'm in the area: I think
  this would help people understand what the read receipt avatars
  are.
diff: @@ -170,15 +170,15 @@ module.exports = React.createClass({
  let title;
  if (this.props.timestamp) {
  - let suffix = " (" + this.props.member.userId + ")";
  + const prefix = "Seen by " + this.props.member.userId + " at ";
  let ts = new Date(this.props.timestamp);
  if (this.props.showFullTimestamp) {
  // "15/12/2016, 7:05:45 PM (@alice:matrix.org)"
  - title = ts.toLocaleString() + suffix;
  + title = prefix + ts.toLocaleString();
  }
  else {
  // "7:05:45 PM (@alice:matrix.org)"
  - title = ts.toLocaleTimeString() + suffix;
  + title = prefix + ts.toLocaleTimeString();
  }
  }
  