[BUGFIX beta] Fix `Ember.isArray` on IE8

The previous code couldn't check correctly.

``` javascript
Ember.isArray([]);
//=> false
```
Updates README.md to get rid of old examples
Merge pull request #4912 from machty/renovate-readme

Updates README.md to get rid of old examples
Merge pull request #4909 from tricknotes/fix-Ember.isArray

Fix `Ember.isArray` on IE8
[BUGFIX beta] Fix ember-runtime suites in IE8.