Add assets to precompile list for rails 4

This commit adds the flash assets to the rails 4 asset pipeline. Otherwise the assets are not precompiled and do not exist in production.

In addition, to make this work in production, I used <a href="https://github.com/alexspeller/non-stupid-digest-assets">non-stupid-digest-assets</a> to create non-digest versions. To do so, I included this in an initializer:

```ruby
NonStupidDigestAssets.whitelist += ['expressInstall.swf', 'open-flash-chart.swf', 'VERSION.txt', 'swfobject.js']
```

It might make sense to depend on `non-stupid-digest-assets` and add the appropriate files to the whitelist inside ofc2.