Don't push childViews if undefined/invalid (issue #2967)

Since 3a16e2821d021a2c88ac290516825ca3b0cafa62, pushObjects throws an error when provided with null or undefined.

Checking the childViews property for compatibility with the pushObjects method prior to calling pushObjects. Will not attempt to push invalid objects.
Simplified to existence check

As suggested by @stefanpenner
Merge pull request #2975 from realityendshere/fix-childview-pushobjects

Don't push childViews if undefined/invalid (issue #2967)
fix code styling for consistency
Merge pull request #2999 from tchak/fix-style

fix code styling for consistency
use Ember.K for consistency

Unless there's a reason behind using just `function() {}`, it seems more reasonable to use Ember.K for consistency
upload prod builds to s3
Merge pull request #3003 from fivetanley/upload-prod-builds

upload prod builds to s3
Merge pull request #3001 from raulbrito/patch-3

use Ember.K for consistency
Fix: didInsertElement was fired twice

Happens when a ContainerView is created during the didInsertElement event of
its parent ContainerView
Support indeterminate property in checkboxes
Merge pull request #3004 from alexspeller/bind-indeterminate-attribute-in-checkbox

Support indeterminate property in checkboxes
Fixed incorrect example of multi-arg registerBoundHelper