Since the library's only dependency on angular2 is dependency injection, it could be moved into its own module so that it doesn't add more bytes to the angular 2 bundle for users who may not need it.

May be impacted by #2379, so this task should wait until that's resolved to determine the best approach.

TODO:

• Move files and update imports (unit tests and e2e tests should be passing)
• Create package.json with unique npm package name
• Make typings build step include angular2/angular2_http as separate d.ts file
• Make sure pub release script will correctly publish package (manually test by installing in an application)
• Make sure npm release script will correctly publish module (manually test by installing in an application)
• Add index.ts & index.dart at top-level of angular2_http
• Update paths in all docs
• Check angular.io docs output
• Add README to base directory
• Confirm that bundle/distribution are created consistently with Angular2
• Change ambient module name output in d.ts and bundles to ngHttp
• Add step in npm distribution to include http directory in angular2 package
• Rename angular2_http.ts to http.ts