[exclude_platform] Suite has an excludes attr for platform names to go
[exclude_platform] don't load instances where platform excluded
[exclude_platform] excludes will default to an empty array
[exclude_platform] spec for load_instances not grabbing excluded platforms
[exclude_platform] spec for suite.rb, excludes should default to []
Include Config's object_id in the actor name.

It may be possible to instantiate multiple Kitchen::Config objects in
one Ruby process. With this addition, there should be a way for a Config
object to kill only its own instance actors.
Add InstanceActor class which is an actor delegate for Instance.

There are several reasons for this change:

* Previously an actor (with its own thread) was created for every
  instance whether or not it was used. This includes simply running the
  list subcommand or generating an instance list for the vagrant driver.
* A subset of instances are usually supplied via the CLI so not all
  instances need to become a full actor.
* Serial mode doesn't need the extra threading, it can use simple
  Instance objects.

As a result the following API changes affect Kitchen::Config:

* Config#instances returns lightweight Instance objects which are no
  longer Celluloid actors. This collection is memoized in the Config
  object for fast recall.
* A new method Config#instance_actors(regex = nil) is added to return
  Celluloid actors in the form of InstanceActor objects. Only those
  instances that match the regex will be created, thus cutting down on
  the quantity of extra unused threads.
Merge remote-tracking branch 'sandfish8/exclude_platform' into 1.0

Conflicts:
	lib/kitchen/config.rb
	spec/kitchen/config_spec.rb
Whitespace.