* fix: fix listeners list inherit race of conditions (#395)

Fix issue because of which listener from which listenres has been inherited able to
clean it before new listener will get that list (because new one make call on async
private queue).

* Removing version under the supported platform (#397)

* fix(subscriber): fix subscribe request timeout missing 'reconnect' event (#398)

When maximum subscribe request idle timeout reached, request fail with
timeout error. PubNub SDK report unexpected disconnection and retry
request. Because of issue (fixed) 'reconnect' event will be sent only at double
time of configured subscribe request idle time (CE-3744)

fix(configuration): fix heartbeat value on configuration copy

Event when value not has been set, it was reset to minimum value (20) on
configuration object copy. This has been fixed by direct assign to ivar.

fix(documentation): fix outdated configuration object inline help documentation

Fix default origin and minimum heartbeat value information in PNConfiguration
header.