README.md: moved from README

Change-Id: I462aa8395d25e571868604583111855377c58b07
Reviewed-on: https://go-review.googlesource.com/63510
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
Reviewed-by: Nigel Tao <nigeltao@golang.org>
diff --git a/README b/README.md
similarity index 100%
rename from README
rename to README.md