init Follow Blogs immediately

Since the 'bp-follow-blogs.php' file is included during the `bp_loaded` action, there's no need to hook `bp_follow_blogs_init()` to `bp_loaded`. Indeed, doing so produces anomalies in the `bp_loaded` callback array such that the priority order is messed up. See https://core.trac.wordpress.org/ticket/27428

It'd be nice if there were a `do_action( 'bp_follow_blogs_loaded' )` following the init so an extension of an extension of an extension of an extension can be notified :-)