fix: Add git tag to CocoaPods source property (#601)

This change will make the CocoaPods version which is installed match the NodeJS version used.  
Currently, CocoaPods will install the latest version on head which could not match the JavaScript version of the library.

Changes:

1. Use the version tag to match the version installed by CocoaPods to that coming the from the `package.json` file.

RNFastImage.podspec

@@ -12,10 +12,10 @@ Pod::Spec.new do |s|
   s.platforms     = { :ios => "8.0", :tvos => "9.0" }
   s.framework     = 'UIKit'
   s.requires_arc  = true
-  s.source        = { :git => "https://github.com/DylanVann/react-native-fast-image.git" }
+  s.source        = { :git => "https://github.com/DylanVann/react-native-fast-image.git", :tag => "v#{s.version} }
   s.source_files  = "ios/**/*.{h,m}"
 
   s.dependency 'React'
   s.dependency 'SDWebImage', '~> 5.0'
   s.dependency 'SDWebImageWebPCoder', '~> 0.2.3'
-end
+end