Fix an issue where messages retried across a transport upgrade could theoretically lead to duplicate messages #308
Fix an issue where a client-detectable auth error on connect could cause the connect attempt to fail after the connect timeout (15s) rather than immediately #314
No net changes. 0.8.25 reverted a new header addition due to Ably not yet sending the correct access-control-allow-headers CORS headers for it; 0.8.26 re-adds it.