fix failing test on IE11.

turns out the internal escaping stragety can differ between browsers. We
should defer to the browsers defaults
Fix then, than comment typo
Merge pull request #5519 from maximerassi/patch-1

Fix then, than comment typo
Merge pull request #5518 from stefanpenner/IE11

fix failing test on IE11.
Improve wording of documentation for getProperties()
Merge pull request #5520 from mostwanted1976/patch-1

Improve wording of documentation for getProperties()
Fixes the function name

Related to this [PR](https://github.com/emberjs/ember.js/pull/5513).
Merge pull request #5521 from twokul/rename-function

Fixes the function name
[BUGFIX beta] Do not use defineProperty on each View instance.
Merge pull request #5523 from rwjblue/do-not-define-property-too-much

[BUGFIX beta] Do not use defineProperty on each View instance.
Cleanup platform
Merge pull request #5528 from krisselden/platform-cleanup

Cleanup platform
Change ENV.MANDATORY_SETTER to FEATURES so it can be compiled out of production builds.
Merge pull request #5529 from krisselden/mandatory-setter-as-feature

Mandatory setter as feature
Revert inadvertent Brocfile changes.

Changes were made in cc39229.
Cleanup enumerable
Merge pull request #5541 from knownasilya/uniq

Cleanup enumerable mixin
More ES3 fixes.

Still need to conditionally switch on browsers that do not have ES5 compliant accessors, because isEnabled is compiled out based on development vs production build.
Merge pull request #5535 from krisselden/mandatory-setter-es3-fix

Fix for ES3 browsers in development mode.
[DOC] Small grammar fix on enumerable filter method