guess() method returns Asia/Manila when the timezone is Australia/Perth

[niyaza3]

In internet explorer guess() is returning Asia/Manila instead of Australia/Perth.

[ichernev]

Try to figure out if guess is using Intl (not sure if IE has Intl), or not. If guess is using our custom "smart" implementation, then check how different these timezones are. Also, it's possible IE is buggy and reports wrong offsets which confuse moment-timezone.

There is a reason it's called guess and not getTimezone, because its best effort and could fail for a number of reasons.

Closing this in favor of #873.