Added a readme to the browser package, so people know what's up.
Added a readme to the browser package, so people know what's up.

Review URL: https://codereview.chromium.org//12212138

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@18532 260f80e4-7a28-3924-810f-c04153c831b5

dart-archive/browser