Twitter::Cursor is Enumerable; just call to_a

There’s certainly no need for you to write your own recursive function. The whole point of the `Twitter::Cursor` class is to encapsulate the logic of how to iterate through results.

That’s why `Twitter::Cursor#next_cursor` is a private method. As a rule, you should never need to use the `#attrs` method on any `Twitter` object. I’ve made the raw data available for contingency purposes but it’s almost always an indication that you’re doing something wrong.

I’ve also taken this opportunity to add a bit more parallelism to `twitter-intersect` and remove the global `$client` variable, just to make @rodjek happy.