Use delegation for activity stream Read More links

This ensures that dynamically added items (as when loading more items on a
page via AJAX) will register click events.

Fixes #4782

Props sbrajesh, burakali

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7610 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
1.9 props list update

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7611 cdf35c40-ae34-48e0-9cc9-0c9da1808c22