Now that we have a separate internal rails_to_json, use a separate circular reference stack instead of sticking it in the options hash

    Example: ActiveSupport::JSON.backend = "JSONGem"

  All internal Rails JSON encoding is now handled by ActiveSupport::JSON.encode().  Use of #to_json is not recommended, as it may clash with other libraries that overwrite it.  However, you can recover Rails specific functionality
  if you really want to use #to_json.

    gem 'json'
    ActiveSupport::JSON.backend = "JSONGem"

    class ActiveRecord::Base
      alias to_json rails_to_json
    end

TimeWithZone#advance: leverage Hash#values_at and non-block form of #any? for a little less line noise, and a slight speedup (thanks raggi and Roman2K)

Signed-off-by: NPratik Naik <pratiknaik@gmail.com>

Add thorough tests for Time-object #past?, #future? and #today. Fix TimeWithZone #today? to use #time instead of #utc for date comparison. Update changelog. [#720 state:resolved]

Introduce convenience methods past?, today? and future? for Date and Time classes to facilitate Date/Time comparisons.

Get rid of 'Object#send!'. It was originally added because it's in Ruby 1.9, but it has since been removed from 1.9.
Signed-off-by: NJeremy Kemper <jeremy@bitsweat.net>

Conflicts:

	actionpack/test/controller/layout_test.rb

Fix TimeWithZone unmarshaling: coerce unmarshaled Time instances to utc, because Ruby's marshaling of Time instances doesn't respect the zone

TimeWithZone: when crossing DST boundary, treat Durations of days, months or years as variable-length, and all other values as absolute length. A time + 24.hours will advance exactly 24 hours, but a time + 1.day will advance 23-25 hours, depending on the day. Ensure consistent behavior across all advancing methods.

Signed-off-by: NPratik Naik <pratiknaik@gmail.com>

TimeWithZone: date part getter methods (#year #mon #day etc) are defined on class; no longer relying on method_missing

Signed-off-by: NPratik Naik <pratiknaik@gmail.com>