Upgrade zen-observable to 0.9.0

[nyteshade]

@benjamn When you get a chance, can you bump zen-observable here and in the @apollo/client to use the 0.9.0 release which features the new Observable.all() feature? Additionally, npmjs.org only shows 1.1.0 so there needs a deployment there as well.

[nyteshade]

Putting together a PR. The new build of zen-observable releases a class based Observable, not a function based one. This means that all the Observable tests largely fail or are useless. This would have implications for any downstream users that for some reason did not invoke Observable with new() or one of the other methods like Observable.of()

[nyteshade]

Actually @benjamn I could use your input on this. I've been chatting with the author of zen-observable. His newer versions export a class Observable and not a var Observable = function(). This means the test cases in this repo are unnecessary or that they would all fail.

I can simply put up a PR that bumps the version and kills the tests or we have to wait. I have recommended that @zenparsing refrain from making that change until a 1.0.0 release for SemVer reasons but its pretty unrealistic to treat Observable like a function when its intent has always been for it to be a class. What are your thoughts on how to handle this here in zen-observable-ts?