Add podspec

+Pod::Spec.new do |s|
+  s.name         = "PNChart"
+  s.version      = "0.1.8"
+  s.summary      = "A simple and beautiful chart lib with animation used in Piner for iOS"
+
+  s.homepage     = "https://github.com/kevinzhow/PNChart"
+  s.screenshots  = "https://github-camo.global.ssl.fastly.net/ea8565b7a726409d5966ff4bcb8c4b9981fb33d3/687474703a2f2f646c2e64726f70626f7875736572636f6e74656e742e636f6d2f752f313539393636322f706e63686172742e706e67"
+
+  s.license      = { :type => 'MIT', :file => 'LICENSE' }
+
+  s.author       = { "Kevin" => "kevinchou.c@gmail.com" }
+
+  s.platform     = :ios, '6.0'
+  s.source       = { :git => "https://github.com/kevinzhow/PNChart.git", :tag => s.version.to_s }
+
+  s.source_files = 'PNChartDemo/PNChart/*.{h,m}'
+  s.public_header_files = 'PNChartDemo/PNChart/*.h'
+  s.frameworks   = 'CoreGraphics', 'UIKit', 'Foundation', 'QuartzCore'
+  s.requires_arc = true
+end