leading slash confuses non-git tools that read .gitignore, like ag

BUG=
R=scroggo@google.com

Author: mtklein@google.com

Review URL: https://chromiumcodereview.appspot.com/21055005

git-svn-id: http://skia.googlecode.com/svn/trunk@10439 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/.gitignore b/.gitignore
index d653a17..b44f4da 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,7 +3,7 @@
 .DS_Store
 .gclient*
 *.pyc
-/gyp/build/
-/out/
-/third_party/externals/
-/xcodebuild/
+gyp/build/
+out/
+third_party/externals/
+xcodebuild/