Make static test site.

Running the following from the ember repo should result in a static file to
run the test suite on:

Rake task:

```
rake ember:generate_static_test_site
```

Manually (make sure to run `rake dist` first):

```ruby
require 'bundler/setup'
require 'ember-dev'

generator = EmberDev::TestSiteGenerator.new(static: true) 
generator.save('dist')
```

This is an initial step in getting Sauce Labs integration working. Once
we have a static site for our tests, we can use Sauce Lab's REST API to
manage jobs.

Using this static site results in a fully passing suite under both Chrome and Safari (for Ember).