Auto reconnect and bug fixes

Added features

Auto reconnect WebSocket connection in case of network failure. Refer README for usage details -
https://github.com/rainmattertech/pykiteconnect#websocket-usage

Bug fixes

1. Fixed mode was sent incorrectly as quote while subscribed for full mode (3d78dfc)
2. Send empty buy and sell lists instead of empty depth if depths are not available. (1c2e0cd)