update changelog to unreleased 1.3.1
update changelog to unreleased 1.3.1

influxdb/influxdb,mark-rushakoff/influxdb,influxdata/influxdb,influxdb/influxdb,nooproblem/influxdb,nooproblem/influxdb,influxdb/influxdb,influxdb/influxdb,mark-rushakoff/influxdb,influxdb/influxdb,nooproblem/influxdb,nooproblem/influxdb,mark-rushakoff/influxdb,influxdb/influxdb,li-ang/influxdb,mark-rushakoff/influxdb,influxdata/influxdb,li-ang/influxdb,nooproblem/influxdb,mark-rushakoff/influxdb,mark-rushakoff/influxdb