- resuming video when unplugging headphones

https://trello.com/c/mKVuSxN7/150-bug-unplugging-headphones-from-an-ios-
device-during-video-ad-playback-causes-the-video-to-pause-with-debug-log
-messages-saying-u
- fixed label bug on ios7

https://trello.com/c/fm2X3Bvo/74-iphone-5-or-4s-the-text-you-can-skip-th
Add visual support for iOS staging server build
Merge branch 'master' of https://github.com/Applifier/unity-ads
Debug logging off by default
Merge branch 'headphonesUnpluggedBug'

Conflicts:
	ios/UnityAds/UnityAdsVideo/UnityAdsVideoViewController.m
- missing property added

- import section fixed
Release 1.3.9
Merge branch 'master' of https://github.com/Applifier/unity-ads
Merge branch 'master' into network-selection