update checkpoints for release at 28400
update checkpoints for release at 28400

coinkeeper/2015-04-19_21-08_bitmark,coinkeeper/2015-04-19_21-08_bitmark,coinkeeper/2015-04-19_21-08_bitmark,coinkeeper/2015-04-19_21-08_bitmark,coinkeeper/2015-04-19_21-08_bitmark