0.0.20

• use op batch instead of op event for batching ops, to prevent conceptual atomic transactions such as object moving from being tear apart into string editing, causing rendering issue.
• separate sharedb bundle tool from build script to a standalone package.json

0.0.19

• support interval option in ping api, and pingInterval option in ews constructor.
• change minimal ping interval from 60s to 20s.

0.0.18

• watch for Connection errors so caller can handle those errors.

0.0.17

• prevent calling close and send without _ws
• make close-handler work only if event source = _ws
• use on instead of addEventListener for offline event

0.0.16

• due to untrustable close event, we move close event handler to a standalone function, and call it from both close and offline event.

0.0.15

• fire offline event when offline event received from window.
• upgrade dependencies

0.0.14

• support ping function, which send ping message to server every 60s by default if page is visible
• fix bug: status() should query status from _src if this is a scoped ws.

0.0.13

• pass op parameter from middleware submit action to access function for fine-grained access control

0.0.12

• fix bug: ws refresh causes ews losing event handlers.

0.0.11

• fix bug: pipe create new ews which depends on source ws, however source ws may update, may not ready yet,
  lead to unusable piped ews. additional tracing from root ews is added to update the whole ews pipe tree.
• upgrade dependencies