Bumped version to 4.1.2 and added to changelog

+## [4.1.2 - 4.1 patch, on Oct 9th, 2017](https://github.com/rs/SDWebImage/releases/tag/4.1.2)
+See [all tickets marked for the 4.1.2 release](https://github.com/rs/SDWebImage/milestone/17)
+
+#### Fixes
+
+- Fix `SDWebImageDownloaderOperation` not call `done` when use `SDWebImageDownloaderIgnoreCachedResponse` #2049
+- Static `WebP` decoding little enhancement. Do not need create `WebP` iterator for static images #2050
+- Change `finished` check from `equal` to `equal or greater than` to protect accident condition #2051
+
 ## [4.1.1 - 4.1 patch, on Oct 6th, 2017](https://github.com/rs/SDWebImage/releases/tag/4.1.1)
 See [all tickets marked for the 4.1.1 release](https://github.com/rs/SDWebImage/milestone/14)
 

 Pod::Spec.new do |s|
   s.name = 'SDWebImage'
-  s.version = '4.1.1'
+  s.version = '4.1.2'
 
   s.osx.deployment_target = '10.8'
   s.ios.deployment_target = '7.0'

@@ -15,11 +15,11 @@
 	<key>CFBundlePackageType</key>
 	<string>FMWK</string>
 	<key>CFBundleShortVersionString</key>
-	<string>4.1.1</string>
+	<string>4.1.2</string>
 	<key>CFBundleSignature</key>
 	<string>????</string>
 	<key>CFBundleVersion</key>
-	<string>4.1.1</string>
+	<string>4.1.2</string>
 	<key>NSPrincipalClass</key>
 	<string></string>
 </dict>