1.8 compatibility changes

For comparison with #152 and #147
Not a big deal either way, but I prefer to keep as few distractions in a codebase as possible. Side benefit of adding it to your `.vimrc` is not having to ever add it to a `.simplecov` file again. You should be able to add:

```
au BufNewFile,BufRead .simplecov set filetype=ruby
```