1.4.0

Added

• send_events to publish a batch of events over a single connection. Opening a connection costs a TCP and an AMQP handshake, so publishing hundreds of events one at a time spends most of its time connecting
• Tests covering the single connection, the per event messages and the per event tracing spans of send_events

Changed

• send_event publishes through send_events, so there is one publish path. The messages it sends are unchanged
• The producer span of a publish no longer covers opening the connection, only the publish itself