warn that docs/quickstart.md is out of sync with official docs

(SkipBuildbotRuns)
NOTREECHECKS=True
NOTRY=True
R=halcanary@google.com, hcm@google.com, mtklein@google.com
TBR=borenet

Author: epoger@google.com

Review URL: https://codereview.chromium.org/245283002

git-svn-id: http://skia.googlecode.com/svn/trunk@14287 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed