LoadError#path not implemented

I have the following code in my spec helper:

``` ruby
begin
  require 'coveralls'

  SimpleCov.formatter = SimpleCov::Formatter::MultiFormatter[
    SimpleCov::Formatter::HTMLFormatter,
    Coveralls::SimpleCov::Formatter
  ]
rescue LoadError => error
  raise error unless error.path == 'coveralls'
end
```

It does not work on JRuby in 2.0 mode, but works just fine on MRI 2.0 and trunk.
