Ignore the ".bleeding_edge" file.

This file is introduced via Puppet and will be migrated to from
".git_bleeding_edge". In the meantime, ignore it so Git doesn't
think it's an untracked modication.

TBR=iannucci@chromium.org
BUG=chromium:740171
TEST=None

Change-Id: Ia878996c3c32c49e1f7d80293bef55ed0a09dbab
Reviewed-on: https://chromium-review.googlesource.com/565888
Reviewed-by: Daniel Jacques <dnj@chromium.org>
Commit-Queue: Daniel Jacques <dnj@chromium.org>

.gitignore

@@ -22,6 +22,7 @@
 /svn
 /svn.bat
 /svnversion.bat
+/.bleeding_edge
 /.codereview_upload_cookies
 /.gitconfig
 /.git_bleeding_edge