Merge pull request #1186 from kyleknap/s3-grant-doc

Update s3 --grants documentation

awscli/customizations/s3/subcommands.py

@@ -129,7 +129,10 @@
         'Grant specific permissions to individual users or groups. You '
         'can supply a list of grants of the form::<p/>  --grants '
         'Permission=Grantee_Type=Grantee_ID [Permission=Grantee_Type='
-        'Grantee_ID ...]<p/>Each value contains the following elements:'
+        'Grantee_ID ...]<p/>To specify the same permission type for multiple '
+        'grantees, specify the permission as such::<p/> --grants '
+        'Permission=Grantee_Type=Grantee_ID,Grantee_Type=Grantee_ID,...'
+        '</p>Each value contains the following elements:'
         '<p/><ul><li><code>Permission</code> - Specifies '
         'the granted permissions, and can be set to read, readacl, '
         'writeacl, or full.</li><li><code>Grantee_Type</code> - '