Fixes & updates for compass-sinatra sample project

[adamesque]

Hey Chris,

Here's a handful of fixes to hopefully make this Sinatra sample project a little easier to get started with.

Removing the compiled css file from /static is probably the most helpful change, because if it's present, Sinatra will serve that instead of recompiling the source sass file.

The other potentially helpful change swaps out sass syntax for scss. Not only do most of the tutorials these days seem to use scss, but I, uh, couldn't even get the sass version working. That might just be me not being familiar enough with sass to update it properly.

The other changes are mostly cosmetic.

Left unresolved by this pull request:

• Running compass compile will once again prevent Sinatra from ever recompiling, by regenerating the static file
• It seems like the "right" way to integrate Sass with Sinatra these days is to use Sass's Rack plugin, but that might be a little advanced for this sample project.

Thanks,
Adam