Bugfix: SectionFooterView AutoDimension Support

Problem:
1. I noticed our app was manually laying out subviews in our sectionFooters when I didn't see the need to.

2. After recent changes, Group tableView's which had nil section extremity defaulted to zero, which drops the standard spacing between sections. Note in attatchment.

Notable info:
Statics currently has deploy target of iOS8, which did not yet support automatic sectionFooterView dimensioning.

Solution:
- Offer autosizing option which uses UITableViewAutomaticDimension rather than view's original bounds height. Retain original .view(_) case in the event some clients were already sizing beforehand limiting integration breaks. This also offers automatic margin adherence.
- Bump deploy target to iOS9 for clean integration.
- Revert 2 previous PRs
- Default height for plain/grouped styles to play friendly with tableView's defaults.

Static.xcodeproj/project.pbxproj

@@ -436,7 +436,7 @@
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
-				IPHONEOS_DEPLOYMENT_TARGET = 8.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				MTL_ENABLE_DEBUG_INFO = YES;
 				ONLY_ACTIVE_ARCH = YES;
 				SDKROOT = iphoneos;
@@ -481,7 +481,7 @@
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
-				IPHONEOS_DEPLOYMENT_TARGET = 8.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				MTL_ENABLE_DEBUG_INFO = NO;
 				SDKROOT = iphoneos;
 				SWIFT_VERSION = 3.0.1;

Static/DataSource.swift

@@ -204,7 +204,7 @@ extension DataSource: UITableViewDataSource {
     }
 
     public func tableView(_ tableView: UITableView, heightForHeaderInSection sectionIndex: Int) -> CGFloat {
-        return section(at: sectionIndex)?.header?.viewHeight ?? UITableViewAutomaticDimension
+        return section(at: sectionIndex)?.header?.viewHeight ?? tableView.style.defaultSectionExtremityHeight
     }
 
     public func tableView(_ tableView: UITableView, titleForFooterInSection sectionIndex: Int) -> String? {
@@ -216,7 +216,7 @@ extension DataSource: UITableViewDataSource {
     }
 
     public func tableView(_ tableView: UITableView, heightForFooterInSection sectionIndex: Int) -> CGFloat {
-        return section(at: sectionIndex)?.footer?.viewHeight ?? UITableViewAutomaticDimension
+        return section(at: sectionIndex)?.footer?.viewHeight ?? tableView.style.defaultSectionExtremityHeight
     }
 
     public func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
@@ -283,3 +283,12 @@ extension DataSource: UITableViewDelegate {
         }
     }
 }
+
+extension UITableViewStyle {
+    var defaultSectionExtremityHeight: CGFloat {
+        switch self {
+        case .plain: return 0
+        case .grouped: return UITableViewAutomaticDimension
+        }
+    }
+}

Static/Section.swift

@@ -13,6 +13,10 @@ public struct Section: Hashable, Equatable {
         /// Custom view for the header or footer. The height will be the view's `bounds.height`.
         case view(UIView)
 
+        // View Sized with autolayout
+        // If Pre iOS11: Requires tableview estimatedSectionHeader/FooterHeight to be > 0
+        case autoLayoutView(UIView)
+
         var _title: String? {
             switch self {
             case .title(let extremityTitle): return extremityTitle
@@ -23,12 +27,16 @@ public struct Section: Hashable, Equatable {
         var _view: UIView? {
             switch self {
             case .view(let extremityView): return extremityView
+            case .autoLayoutView(let extremityView): return extremityView
             default: return nil
             }
         }
 
-        var viewHeight: CGFloat? {
-            return _view?.bounds.height
+        var viewHeight: CGFloat {
+            switch self {
+            case .title(_), .autoLayoutView(_): return UITableViewAutomaticDimension
+            case .view(let view): return view.bounds.height
+            }
         }
     }