Dict.each() allows to iterate through values and keys of a Dict.
The callback function is passed value as the first parameter to
be similar to _.each()'s calling sequence.
(imported from commit e745e8b5d2f167b8b8acf7542b767494e354b037)
There are also one or two places we don't need to use it for security
purposes, but we do so for consistencey.
(imported from commit aa111f5a22a0e8597ec3cf8504adae66d5fb6768)
Steve Howell
Zev Benjamin