Fixed resources path in vungle sdk

Old:
 s.resources  = 'vungle/lib/vunglepub/resources'
New:
  s.resources  = 'vungle/lib/vunglepub/resources/*.png'

Without this '/*.png' in path it completely broke build in  Step: Copy Pods Resources 
looks like script Pods-resources.sh does not work properly with folder paths
Please review it.