Handle exceptions during purchase flow

If user leaves application (press home button, etc) during purchase
flow, there will be a null exception.
The may causes by a duplicated call to onCreate() function.
logDebug should be false by default
Merge from upstreams
Handle error if IabActivity is destroyed during purchase flow.

The activity may be destoryed by some abnormal opertaions.
Like exiting application (by pressing home button) then clicking the app
icon to re-enter.
Fix indent.

Fix indent tabs to spaces.
Fix callback paramter from IabHelper

IabHelper won't send item sku back if the item is already owned. Fix it
like.
Revert 8f80b9fd0c4790ac6627fe4531c92a8b6b713db7
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge from 'upstream/master'
Add interface for async consume.
Merge pull request #37 from HolymarsHsieh/ConsumeAsync

Add interface for asynchronizely consume item.