Minor Bluetooth fixes

[cgst]

Addresses #106, but maybe having a configurable flag that defaults to true is better instead
Addresses #107

[cgst]

This seems to block PermissionScope.show() at
while self.waitingForBluetooth ...

[cgst]

I've updated this to ask for bluetooth permissions without calling start/stop advertising, and without blocking the main thread.

The iOS Bluetooth permission dialog seems to trigger only once per bundle ID; restarting/reinstalling the app doesn't trigger it again.

[nickoneill]

@felix-dumit This commit (from issue #107) replaces the call to start/stop advertising with just creation of the bluetooth manager. This seems to request the permission just fine for me but I recall something about this in your original commit for bluetooth support. Was there some situation that required the start/stop calls?

[felix-dumit]

So I tested and it did work, but I could swear before by just instantiating the manager the system permission would not show up.
Finally I remembered that when I was developing I was testing using the Objc-Example and that in fact is the issue here.
By running the swift example it works but not for obj-c. (I'm not sure why this is though)

So probably the best solution to fix #107 is to check in triggerBluetoothStatus if the manager is .PoweredOn otherwise wait for the update in peripheralDidUpdateState and only then start/stop advertising (if powered-on)
Also what concerns me a bit with this is the removal of the waitingForBluetooth because previously we could have the permission alert flash while the bluetooth status was still in process of going from .Unknown to .Authorized.

[nickoneill]

Thanks for the feedback @felix-dumit, I'll check this out in the objc example.

We do have some plans to behave differently for async permissions requests, such as cloudkit. Maybe best to wrap the removal of waitingForBluetooth into that.

[felix-dumit]

Sounds good. I was thinking maybe it would make sense to wrap the results of the status callbacks using a promise or future.

[nickoneill]

I just defaulted the bluetooth power alerts to off, this'll be in the next 1.0.2 release. The other two issues here are broken out into #132 and #133