resolve typo

I think this happened when I was resolving a merge conflict, and I confused the naming from previous/new along the way. Thanks @jwzimmer!

Fixes #1652

src/views/messages/container.jsx

@@ -131,7 +131,7 @@ var Messages = React.createClass({
                 messages={this.props.messages}
                 adminMessages={this.props.adminMessages}
                 scratcherInvite={this.props.invite}
-                numNewMessages={this.props.numNewSocialMessages}
+                numNewMessages={this.props.numNewMessages}
                 handleFilterClick={this.handleFilterClick}
                 handleAdminDismiss={this.handleMessageDismiss}
                 loadMore={loadMore}