[AnkitaAdvitot]

Description

Fixes #237

In kiteconnect/ticker.py, KiteTickerClientProtocol._loop_ping was scheduled during onOpen to maintain connection health and refresh _last_ping_time. However, the method only scheduled the next callback and never transmitted a ping frame (self.sendPing() was never called).

Because of this:

1. self._last_pong_time remained None indefinitely, rendering the _loop_pong_check connection drop detector inactive.
2. Silent network drops (e.g. WiFi/ISP drop without TCP RST) left the socket in an undetected zombie state until OS TCP timeouts killed it.

Solution

1. Call self.sendPing() inside _loop_ping() when self.state == self.STATE_OPEN, wrapped in a safe try...except block.
2. Initialize self._last_pong_time = time.time() in onOpen() so timeout tracking starts immediately from handshake completion.
3. In onClose(), safely check DelayedCall.active() before cancelling _next_ping and _next_pong_check.
4. Add unit tests in tests/unit/test_ticker.py verifying that:
   • _loop_ping invokes sendPing and updates _last_ping_time.
   • _loop_pong_check calls dropConnection when pong timeout is exceeded.
   • _loop_pong_check remains connected when heartbeats are healthy.
   • onOpen initializes _last_pong_time and triggers _loop_ping.