list all other guss files, and some styles

Greg, I've added a new function to list all of the files and some of their data when someone builds a new spreadsheet. I've also added some preliminary styles, found in `static/css/site.css` so we don't have to stare at this blank page any more :dancer: 

![screen shot 2014-12-13 at 10 21 44 am](https://cloud.githubusercontent.com/assets/1943001/5424735/1b03c966-82b2-11e4-8fd8-9806304e3df1.png)

I don't think this is the best route to go in terms of functionality - I guess I'd like to see two buttons instead of one. One would be the current "build new guss" - the second would be "view all guss documents" since the only way to view the docs is by creating another document.

### `show_other_gus_files()`

The new function `show_other_gus_files()` isn't terribly elegant, since it makes a unique call to the `gapi` for every single item, since the `'path': '/drive/v2/files/' + folder + '/children'` for returning all of those files only returns the `id` and not the file name. Could we request more information to be returned with that?