GitLab

- Remove unnecessary additional instructions for Mac
- Delete hand-generated getstarted.zip file

BUG=64259
TEST=none

Review URL: http://codereview.chromium.org/6126005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@71722 0039d316-1c4b-4281-b951-d872f2087c98