add cocoaspods suports

Author: daiweilai

DDRichText.podspec

@@ -0,0 +1,12 @@
+Pod::Spec.new do |s|
+  s.name         = "DDRichText"
+  s.version      = "1.0.0"
+  s.summary      = "Just like Weixin Moment and Weibo RichText"
+  s.homepage     = "https://github.com/daiweilai/DDRichText"
+  s.license      = "Apache License"
+  s.author       = { "David Day" => "[email protected]" }
+  s.source       = { :git => "https://github.com/daiweilai/DDRichText.git", :tag => 'v1.0.0'}
+  s.source_files = 'DDRichTextLib','DDRichTextLib/**/*.{h,m}'
+  s.requires_arc = true
+  s.platform     = :ios, '7.0'
+end