Fix issue with reloading data

When using PagingViewControllerDataSource, the reloadData(around:)
method would not update the menu items, as it was caching the old
items in the interal IndexedDataSource instance.

Parchment/Classes/IndexedPagingDataSource.swift

@@ -3,13 +3,9 @@ import Foundation
 class IndexedPagingDataSource<T: PagingItem>:
   PagingViewControllerInfiniteDataSource where T: Hashable & Comparable {
 
-  let items: [T]
+  var items: [T] = []
   var viewControllerForIndex: ((Int) -> UIViewController?)?
 
-  init(items: [T]) {
-    self.items = items
-  }
-
   func pagingViewController<U>(
     _ pagingViewController: PagingViewController<U>,
     viewControllerForPagingItem item: U) -> UIViewController {

Parchment/Classes/PagingViewController.swift

@@ -321,11 +321,8 @@ open class PagingViewController<T: PagingItem>:
   /// - Parameter pagingItem: The `PagingItem` that will be selected
   /// after the data reloads.
   open func reloadData(around pagingItem: T) {
-    stateMachine.fire(.select(
-      pagingItem: pagingItem,
-      direction: .none,
-      animated: false))
-    reloadItems(around: pagingItem)
+    indexedDataSource?.items = generateItemsForIndexedDataSource()
+    select(pagingItem: pagingItem, animated: false)
   }
 
   /// Selects a given paging item. This need to be called after you
@@ -521,21 +518,24 @@ open class PagingViewController<T: PagingItem>:
       }
     }
   }
-  
-  private func configureDataSource() {
+
+  private func generateItemsForIndexedDataSource() -> [T] {
     let numberOfItems = dataSource?.numberOfViewControllers(in: self) ?? 0
-    let items = (0..<numberOfItems).enumerated().flatMap {
+    return (0..<numberOfItems).enumerated().flatMap {
       dataSource?.pagingViewController(self, pagingItemForIndex: $0.offset)
     }
-
-    indexedDataSource = IndexedPagingDataSource(items: items)
+  }
+
+  private func configureDataSource() {
+    indexedDataSource = IndexedPagingDataSource()
+    indexedDataSource?.items = generateItemsForIndexedDataSource()
     indexedDataSource?.viewControllerForIndex = { [unowned self] in
       return self.dataSource?.pagingViewController(self, viewControllerForIndex: $0)
     }
-    
+
     infiniteDataSource = indexedDataSource
-
-    if let firstItem = items.first {
+    
+    if let firstItem = indexedDataSource?.items.first {
       select(pagingItem: firstItem)
     }
   }