Fix wrong unix time check when checking the updater.
Fix unit test bootstrap.

For some reason, the BP Follow revision date doesn't appear to stick in the
database like BuddyPress' options do.  When running subsequent unit tests,
dbDelta errors pop up due to the DB date not sticking, but the BP Follow
table still persists.

To workaround this, this commit drops the BP Follow table during the
bootstrap to prevent these dbDelta errors.

The BP Follow table is also now installed before loading up BP Follow.

See #42.
Support querying following and followers by WP's date query.

Uses the same syntax as the 'date_query' array parameter. See:
http://codex.wordpress.org/Class_Reference/WP_Query#Date_Parameters

Pass 'date_query' parameter to $r['query_args'] array in
bp_follow_get_following() or bp_follow_get_followers().

See #40.