Add CocoaPods support for tvOS

.travis.yml

@@ -1,6 +1,8 @@
 
 language: objective-c
 
+osx_image: xcode7.1
+
 before_install:
 
     - export LANG=en_US.UTF-8

SDWebImage.podspec

@@ -1,7 +1,8 @@
 Pod::Spec.new do |s|
   s.name = 'SDWebImage'
   s.version = '3.7.3'
-  s.platform = :ios, '5.0'
+  s.ios.deployment_target = '5.0'
+  s.tvos.deployment_target = '9.0'
   s.license = 'MIT'
   s.summary = 'Asynchronous image downloader with cache support with an UIImageView category.'
   s.homepage = 'https://github.com/rs/SDWebImage'
@@ -24,9 +25,11 @@ Pod::Spec.new do |s|
   s.subspec 'Core' do |core|
     core.source_files = 'SDWebImage/{NS,SD,UI}*.{h,m}'
     core.exclude_files = 'SDWebImage/UIImage+WebP.{h,m}'
+    core.tvos.exclude_files = 'SDWebImage/MKAnnotationView+WebCache.*'
   end
 
   s.subspec 'MapKit' do |mk|
+    mk.ios.deployment_target = '5.0'
     mk.source_files = 'SDWebImage/MKAnnotationView+WebCache.*'
     mk.framework = 'MapKit'
     mk.dependency 'SDWebImage/Core'