Component sendAction code sample

I think that the API evolved and the code sample wasn't adapted, right?
[NICETHING beta] helpful whitespace classNameBindings assert

I've trolled myself many times thinking that 
classNameBindings works with a space separated string
(probably because of how bind-attr class="" works).
This should help me never troll myself again.

/cc @ebryn
Failing test for the issue #3994.
Merge pull request #4037 from diogomafra/arrayComputed-error

Failing test for the issue #3994.
Improve `reduceComputed` array check assertion.

In #4078 the problem is that `reduceComputed` cannot be used against
non-extended native arrays as we cannot `addArrayObserver`.  `reduceComputed`
used to inform users of this, but no longer does so since support for non-array
dependent keys.  This commit corrects this grievous error.

Fix #4078
Merge pull request #4220 from hjdivad/reduceComputed-complain-bitterly-if-not-ember-array

Improve `reduceComputed` array check assertion.
[BUGFIX release] Allow canceling of Timers in IE8.

For reference:

https://github.com/ebryn/backburner.js/pull/68
https://github.com/ebryn/backburner.js/pull/69
https://github.com/emberjs/ember.js/issues/4222

Fixes #4222.
Merge pull request #4214 from MajorBreakfast/patch-1

Component sendAction code sample
[BUGFIX beta] Do not deprecate the block form of {{render}}.

Fixes #4221.
[BUGFIX beta] Provide helpful error even if Model isn't found.

Previously, you would receive an error if no model was found
corresponding to the route name that you are in. We were already
providing a nice assertion (which lets the user know that the model hook
wasn't defined and can't be inferred), but immediately have that we
would throw an error because we were still calling `find` on a
non-existent model factory.

This simply short curcuits the `find` call if `modelClass` isn't found.
Merge pull request #4208 from rjackson/allow-missing-store-in-model-hook

[BUGFIX beta] Provide helpful error even if modelClass isn't found.
Merge pull request #4217 from machty/classnamebindings-assert

[NICETHING beta] helpful whitespace classNameBindings assert
[BUGFIX beta] reduceComputed fires observers when invalidating with undefined
Merge pull request #4210 from mmun/fix-4197

[BUGFIX beta] reduceComputed fires observers when invalidating with undefined
Merge pull request #4224 from rjackson/do-not-assert-in-render-with-block-template

[BUGFIX beta] Do not deprecate the block form of {{render}}.
Simplify code for action helper

Functionality remains exactly the same.
Merge pull request #4227 from MajorBreakfast/patch-2

Simplify code for action helper
[FEATURE ember-metal-computed-empty-array]

Make `Em.computed.empty` respect arrays automatically, without users having to
know to use `array.[]`.