Ember.get and .set work with global paths in 1.0 mode

@shajith @jish 

When `ACCESSORS` is set to `"0.9"` or `"0.9-dotted-properties"`,
 * `Em.getPath('Foo.bar')` returns `window.Foo.bar`
 * `Em.setPath('Foo.bar', 'baz')` sets `window.Foo.bar` to `"baz"`

When `ACCESSORS` is set to `"1.0-no-warn"` or `"1.0"`, the `getPath` and
`setPath` versions continued to work, but `get` and `set` didn't work
with global paths. Now they do, just like in Ember 1.0.

This PR also includes two small drive-by fixes:

 * `scripts/browser_tests` had a typo
 * `backported/view_state_tests` was in the wrong package