Add convenience methods to remove action items from the button (#240)

Example/Tests/JJFloatingActionButtonSpec.swift

@@ -531,6 +531,59 @@ class JJFloatingActionButtonSpec: QuickSpec {
                         expect(superview) == snapshot()
                     }
                 }
+
+                context("and all but one item are removed") {
+                    beforeEach {
+                        for (index, item) in actionButton.items.enumerated() {
+                            if index > 0 {
+                                actionButton.removeItem(item)
+                            }
+                        }
+                    }
+
+                    it("has the correct number of items") {
+                        expect(actionButton.items.count) == 1
+                    }
+
+                    it("looks correct") {
+                        expect(superview) == snapshot()
+                    }
+
+                    it("looks correct when opened") {
+                        actionButton.open(animated: false)
+                        expect(superview) == snapshot()
+                    }
+                }
+
+                context("and the first item is removed") {
+                    var first: JJActionItem!
+                    var result: JJActionItem?
+                    beforeEach {
+                        first = actionButton.items.first
+                        result = actionButton.removeItem(first)
+                    }
+
+                    it("returns the first item") {
+                        expect(result).notTo(beNil())
+                        expect(result) == first
+                    }
+                }
+
+                context("and an item not from the list is removed") {
+                    var result: JJActionItem?
+                    beforeEach {
+                        let item = JJActionItem()
+                        result = actionButton.removeItem(item)
+                    }
+
+                    it("has the correct number of items") {
+                        expect(actionButton.items.count) == 2
+                    }
+
+                    it("returns nil") {
+                        expect(result).to(beNil())
+                    }
+                }
             }
 
             context("when 1 item is added") {

Sources/JJFloatingActionButton.swift

@@ -324,11 +324,32 @@ import UIKit
     ///
     /// - Parameter item: The action item.
     ///
-    /// - Returns: The item that was add. Its configuration can be changed after it has been added.
-    ///
     func addItem(_ item: JJActionItem) {
         items.append(item) // this will call `didSet` of `items`
-        configureButtonImage()
+    }
+
+    /// Remove an action item from the list of items.
+    ///
+    /// - Parameter item: The action item.
+    ///
+    /// - Returns: The item that was removed. `nil` if `item` was not found.
+    ///
+    @discardableResult func removeItem(_ item: JJActionItem) -> JJActionItem? {
+        guard let index = items.firstIndex(of: item) else {
+            return nil
+        }
+        return removeItem(at: index)
+    }
+
+    /// Remove and returns the action item at the specified position in the list of items.
+    ///
+    /// - Parameter index: The index of the action item. `index` must
+    ///   be a valid index of the list of items.
+    ///
+    /// - Returns: The item that was removed.
+    ///
+    @discardableResult func removeItem(at index: Int) -> JJActionItem {
+        return items.remove(at: index)
     }
 
     /// Calls the given closure on each item that is or was added to the floating action button.