Raise minimum deployment version to iOS 8

 * set min deployment version
 * fix compile errors caused by deprications
 * update minimum size constraints on several modal views
 * remove PSTCollectionView
remove PSTCollectionView from acknowledgements
update readme, update sizes of event list view, add event view
remove extra UIWindow object from xib
Remove homemade UUIDString generator
Merge branch 'raise_min_ios_version' into develop