Do not use WeakRef for target in RemoteViews requests.
Fix ConcurrentModificationException in Dispatcher.performSubmit()

Fixes #641
Log when a target is garbage collected and request is canceled

Fixes #642
Merge pull request #681 from lucasr/issue642

Log when a target is garbage collected and request is canceled
Merge pull request #680 from lucasr/issue641

Fix ConcurrentModificationException in Dispatcher.performSubmit()
Merge pull request #650 from square/dimitris/remote-views-target

Do not use WeakRef for target in RemoteViews requests.
merged with squareup/master