Provide local CSS when external CDN fails

Fixes #352

Signed-off-by: Ryan O'Hara <oharar@email.chop.edu>
I believe the `cssLoaded` method can be removed and this code should be simplified into:

```javascript
var requiredCSS = ['bootstrap.css', 'bootstrap-responsive.css', 'font-awesome.css'],
    loadedCSS = document.styleSheets,
    isLoaded;

for (var i = 0; i < requiredCSS.length; i++) {
    isLoaded = _.some(loadedCSS, function(sheet) { 
        return sheet['href'].indexOf(requiredCSS[i]) >= 0; 
    });

    if (isLoaded) continue;

    var localLink = document.createElement('link');
        .setAttribute('rel', 'stylesheet');
        .setAttribute('type', 'text/css');
        .setAttribute('href', '/static/stylesheets/css/' + requiredCSS[i]);
    document.getElementsByTagName('head')[0].appendChild(localLink);
}
```