Update tag in podspec file due to new tag (v2.x.x) namings

Author: manuelblum

BVLinearGradient.podspec

@@ -11,7 +11,7 @@ Pod::Spec.new do |s|
   s.author          = { "Brent Vatne" => "brentvatne@gmail.com" }
   s.ios.deployment_target = '7.0'
   s.tvos.deployment_target = '9.0'
-  s.source          = { :git => "https://github.com/brentvatne/react-native-linear-gradient.git", :tag => "#{s.version}" }
+  s.source          = { :git => "https://github.com/brentvatne/react-native-linear-gradient.git", :tag => "v#{s.version}" }
   s.source_files    = 'BVLinearGradient/*.{h,m}'
   s.preserve_paths  = "**/*.js"
   s.frameworks = 'UIKit', 'QuartzCore', 'Foundation'