Add 76 column reference in git cl upload message

git_cl.py

Index: git_cl.py
diff --git a/git_cl.py b/git_cl.py
index 9a0c612a4ad949f5d638bd122b7f15fc8d5645a6..02f20b5bf8ff7ab727b905ec93c4db4629ef66b0 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -864,6 +864,8 @@ class ChangeDescription(object):
       '# Enter a description of the change.\n'
       '# This will be displayed on the codereview site.\n'
       '# The first line will also be used as the subject of the review.\n'
+      '#----------------------This line is 76 characters long'
+      '----------------------\n'
     ) + self._description
 
     if '\nBUG=' not in self._description: