message: docs: improve the GitHub README.md, update links, etc
diff: [![npm version](https://badge.fury.io/js/%40angular%2Fcore.svg)](https://www.npmjs.com/@angular/core)
  -[![Sauce Test Status](https://saucelabs.com/browser-matrix/angular2-ci.svg)](https://saucelabs.com/u/angular2-ci)
  -
  -*Safari (7+), iOS (7+) and IE mobile (11) are tested on [BrowserStack][browserstack].*
  -
  # Angular
  Angular is a development platform for building mobile and desktop web applications using Typescript/JavaScript and other languages.
  @@ -17,12 +13,19 @@ Angular is a development platform for building mobile and desktop web applicatio
  [Get started in 5 minutes][quickstart].
  +
  +## Changelog
  +
  +[Learn about the latest improvements][changelog].
  +
  +
  ## Want to help?
  Want to file a bug, contribute some code, or improve documentation? Excellent! Read up on our
  guidelines for [contributing][contributing] and then check out one of our issues in the [hotlist: community-help](https://github.com/angular/angular/labels/hotlist%3A%20community-help).
  [browserstack]: https://www.browserstack.com/automate/public-build/LzF3RzBVVGt6VWE2S0hHaC9uYllOZz09LS1BVjNTclBKV0x4eVRlcjA4QVY1M0N3PT0=--eb4ce8c8dc2c1c5b2b5352d473ee12a73ac20e06
  -[contributing]: http://github.com/angular/angular/blob/master/CONTRIBUTING.md
  -[quickstart]: https://angular.io/docs/ts/latest/quickstart.html
  -[ng]: http://angular.io
  +[contributing]: https://github.com/angular/angular/blob/master/CONTRIBUTING.md
  +[quickstart]: https://angular.io/guide/quickstart
  +[changelog]: https://github.com/angular/angular/blob/master/CHANGELOG.md
  +[ng]: https://angular.io
  