[dist] Update package.json and CocoaPods versions to 0.7.0-rc.2

This release includes a fix for ListViews so that they no longer produce a redbox. The versioning uses the "rc.#" style that http://semver.org/ uses.

Also went back to using tags for CocoaPods. Will create the git tag v0.7.0-rc.2 that points to this commit.

React.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name                = "React"
-  s.version             = "0.7.0-rc"
+  s.version             = "0.7.0-rc.2"
   s.summary             = "Build high quality mobile apps using React."
   s.description         = <<-DESC
                             React Native apps are built using the React JS
@@ -18,7 +18,7 @@ Pod::Spec.new do |s|
   s.homepage            = "http://facebook.github.io/react-native/"
   s.license             = "BSD"
   s.author              = "Facebook"
-  s.source              = { :git => "https://github.com/facebook/react-native.git", :commit => "da0a97d" }
+  s.source              = { :git => "https://github.com/facebook/react-native.git", :tag => "v#{s.version}" }
   s.default_subspec     = 'Core'
   s.requires_arc        = true
   s.platform            = :ios, "7.0"