Introduce __defineNonEnumerable hook, this allows parts of ember to opt-out of the enumerable safety. Unfortunately at this time there is not way to create fast non-enumerable properties. Historically ember has this to allow people to merge, extend and JSON.stringify. Unfortunately some things like Ember.Views should do not need this but still suffer from the pretty hefty overhead.

This PR Reduces the cost of view allocation by 300% -> 400%.

Micro bench (creating 10,000 views):

before: 120ms
after:   35ms
[DOCS] Fix bind-attr example code
[BUGFIX beta] Use new transform syntax.

* Update to HTMLBars 0.5.0
* Make AST transforms not require Walker to be imported.
* Add some additional YUIDocs to Transform Factories.
Merge pull request #9848 from knownasilya/patch-2

[DOCS] Fix bind-attr example code
[BUGFIX beta] Allow tagName to be a CP with deprecation
Merge pull request #9905 from mixonic/allow-tagName-cp-with-dep

[BUGFIX beta] Allow tagName to be a CP with deprecation
Merge pull request #9903 from rwjblue/update-htmlbars

[BUGFIX beta] Use new transform syntax.
[BUGFIX beta] Allow view instances in {{view}}
Adding npm-debug.log to gitignore
Merge pull request #9881 from chadhietala/passing-view

[BUGFIX beta] Allow view instances in {{view}}
[BUGFIX beta] Ensure bound attrs flush immediately
Merge pull request #9906 from chadhietala/npm-debug.log

Adding npm-debug.log to .gitignore
Merge pull request #9907 from mixonic/sync-attr-nodes

[BUGFIX beta] Ensure bound attrs flush immediately
failing test showing extra views w/makeBoundHelper
[BUGFIX beta] makeBoundHelper optimized unbound

makeBoundHelper now optimizes unbound parameters.
If none of the values are Streams in params or
the options hash, we can take the performance
fast path and just return a string. This is both
faster and doesn’t create extra view objects.

refs GH-9902
Merge pull request #9909 from fivetanley/make-bound-helper-perf-optimizations

[BUGFIX beta] makeBoundHelper should act as if the helper is unbound when parameters aren't bound. [perf]
[BUGFIX beta] Do not stringify null classes, allow unquoted bind-attr class
Merge pull request #9914 from mixonic/cnb

[BUGFIX beta] Do not stringify null classes, allow unquoted bind-attr class
[BUGFIX beta] Drop classList, treat classes as quoted attributes
[BUGFIX beta] bound if/unless inside unbound if/unless (#9894)