fix(async): create new cache object for each instance by default

[TheSharpieOne]

fix #1236
Previously, the same object was being used by for async cache by
default when no cache was passed to the component. This same object
was used for every instance.
Now, an object is used to determine if the default is being used
and will create a new object for each instance in which no prop
was passed.

If the user wants to have shared cache, they will need to opt-in by providing the same object to the component via the cache prop.

[coveralls]

Coverage increased (+0.01%) to 93.023% when pulling ddd1fbc on TheSharpieOne:fix/remove-shared-cache into 2b14448 on JedWatson:master.

[TheSharpieOne]

@bvaughn, this is related to a change you made recently with #1226. I'm not sure if the shared cache thing was intentional or not. If it was, you can just close this. If it was not intentional, please take a look and hopefully get this in before rc3 (or v1 if there isn't another rc planned).

[somsub]

We are having the same issue and need this change above? Is there a timeframe on this being available?

Thank you @TheSharpieOne for fixing this

[Seldaek]

@somsub as a workaround for now you can just specify your own cache on every instance:

var yourCache = {};
<Select.Async [...]
            cache={yourCache}
/>

Just make sure you somehow define that variable smartly enough that you do get a cache still, but not so broadly that the cache is shared across instances.

[bvaughn]

D'oh! Sorry. This fell through the cracks on my end.

[bvaughn]

Merged with a minor change to move cache prop setting from componentWillMount to the constructor.

[somsub]

Thanks for merging @bvaughn. When will this be released for consumption from npm ?

[bvaughn]

Not sure. I'm at Connect Tech right now (presenting) so I won't be making a release any time over the next few days> Jed or someone else might.

[cpruijsen]

@bvaughn is a release planned? Not having much luck building from sources and requiring locally to use the patched version.