Update podspec and swifttools to 5.4.

Author: ivanvorobei

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.2
+// swift-tools-version: 5.4
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription

SPDiffable.podspec

@@ -1,7 +1,7 @@
 Pod::Spec.new do |s|
 
   s.name          = 'SPDiffable'
-  s.version       = '1.1.7'
+  s.version       = '1.1.8'
   s.summary       = 'Extenshion of Diffable API which allow not duplicate code and use less models.'
   s.homepage      = 'https://github.com/ivanvorobei/SPDiffable'
   s.source        = { :git => 'https://github.com/ivanvorobei/SPDiffable.git', :tag => s.version }