Update README

Fixes crash with nil iTunesURL

README.md

@@ -13,6 +13,8 @@ If a new version is available, an alert can be presented to the user informing t
 - Siren is actively maintained by [**Arthur Sabintsev**](http://github.com/ArtSabintsev) and [**Aaron Brager**](http://twitter.com/getaaron).
 
 ### Changelog
+#### 0.2.3
+- Fixed [Issue #7](https://github.com/ArtSabintsev/Siren/pull/7): a crash when loading the App Store
 #### 0.2.2
 - Fixed [Issue #6](https://github.com/ArtSabintsev/Siren/issues/6): Setting `checkType` to `.Daily` or `.Weekly` now works properly.
 - Other minor internal changes.

Siren.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name         = "Siren"
-  s.version      = "0.2.2"
+  s.version      = "0.2.3"
   s.summary      = "Notify users when a new version of your iOS app is available, and prompt them with the App Store link.."
 
   s.description  = <<-DESC
@@ -15,7 +15,7 @@ Siren is actively maintained by Arthur Sabintsev and Aaron Brager.
   s.license      = "MIT"
   s.authors      = { "Arthur Sabintsev" => "arthur@sabintsev.com", "Aaron Brager" => "getaaron@gmail.com" }
   s.platform     = :ios, "8.0"
-  s.source       = { :git => "https://github.com/ArtSabintsev/Siren.git", :tag => "0.2.2" }
+  s.source       = { :git => "https://github.com/ArtSabintsev/Siren.git", :tag => "0.2.3" }
   s.source_files = 'Siren/Siren.swift'
   s.resources    = 'Siren/Siren.bundle'
   s.requires_arc = true

Siren/Siren.swift

@@ -540,7 +540,7 @@ private extension Siren {
     
     // Actions
     func launchAppStore() {
-        let iTunesString =  "https://itunes.apple.com/app/id\(appID)";
+        let iTunesString =  "https://itunes.apple.com/app/id\(appID!)";
         let iTunesURL = NSURL(string: iTunesString);
         UIApplication.sharedApplication().openURL(iTunesURL!);
     }