Override -[TWTNibBackedView layoutSubviews] to layout contentView

* Override -layoutSubviews in TWTNibBackedView to transparently layout contentView
* Update CocoaPods version number to 0.19

Foundation/Date Range/TWTDateRange.h

@@ -60,7 +60,7 @@ NS_ASSUME_NONNULL_BEGIN
      this date is before the start date.
  @result An initialized date range instance with the specified start and end dates.
  */
-- (instancetype)initWithStartDate:(NSDate *)startDate endDate:(NSDate *)endDate NS_DESIGNATED_INITIALIZER;
+- (instancetype)initWithStartDate:(nullable NSDate *)startDate endDate:(nullable NSDate *)endDate NS_DESIGNATED_INITIALIZER;
 
 
 /*!

TWTToast.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name             = "TWTToast"
-  s.version          = "0.18"
+  s.version          = "0.19"
   s.summary          = "Tools and Utilities for Cocoa Development"
   s.homepage         = "https://github.com/twotoasters/Toast"
   s.license          = { :type => 'MIT', :file => 'LICENSE' }

UIKit/Nib-Backed View/TWTNibBackedView.h

@@ -27,6 +27,8 @@
 #import <UIKit/UIKit.h>
 
 
+NS_ASSUME_NONNULL_BEGIN
+
 /*!
  The TWTNibBacking protocol simply declares the +nib message. This allows users of a class to easily
  get the nib that backs it. This is useful when doing things like, e.g., registering a nib for a
@@ -104,6 +106,8 @@
  @discussion The base implementation of this method does nothing. Subclasses should override this
      if they wish to perform some initialization after the nib has been loaded.
  */
-- (void)didInstantiateObjectsInBackingNib __attribute__((objc_requires_super));
+- (void)didInstantiateObjectsInBackingNib NS_REQUIRES_SUPER;
 
 @end
+
+NS_ASSUME_NONNULL_END

UIKit/Nib-Backed View/TWTNibBackedView.m

@@ -63,6 +63,13 @@ - (void)instantiateObjectsInBackingNib
 }
 
 
+- (void)layoutSubviews
+{
+    [super layoutSubviews];
+    [self.contentView layoutIfNeeded];
+}
+
+
 - (void)didInstantiateObjectsInBackingNib
 {
 }