Add observable query current result

[tmeasday]

This PR is rebased from #635.

It also should not be merged until we've confirmed with RA.

[helfer]

@tmeasday would you like to see this merged+published before or after our refactor?

[tmeasday]

Ideally before I think. Let me hassle @jbaxleyiii again, as he was going to look at this stuff

[jbaxleyiii]

@tmeasday @helfer I'm so sorry for the delayed response on this. Especially since @tmeasday killed it here and with RA. I'm all for it!

[tmeasday]

Good to go then @helfer

[tmeasday]

@helfer - rebased against master.

I actually ended up undoing part of this commit: https://github.com/apollostack/apollo-client/pull//commits/d852946123ccf2c6f5496a60924a67d89a5954c5

My rationale is that QueryManager.getCurrentQueryResult (and things in general) shouldn't need to look at the state of the query in order to figure out what the results of the query are. It's problematic for a few reasons, one in particular is: what if you call it before the query has even initialized, and the state is null? (which I do from observable.currentResult() if you call it right after creating the query).

The state of the query should be irrelevant to the results of the query. It's only the options etc of the query that determine the results. (The state drives loading--and networkStatus later--though of course).

I'm not sure if we should remove the rest of the above commit too? Do we use queryState.stopped for anything else? Probably something for you and @stubailo to look at during the refactor.

Obviously the tests from that #696 are super helpful to have, and still pass in this branch!

cc @rricard

[helfer]

@tmeasday yeah, I think we'll remove the stopped state in the refactor, but I'll publish a version with this first.