Table -> Stradivari

let's move all the generators concerns into the generator themselves.

what should remain here is 

```ruby
def table_for(*args, &block)
  Table::Generator.new(self, *args, &block).to_s
end

def csv_for(*args, &block)
  CSV::Generator.new(self, *args, &block).to_s
end

[...]
```

so every generator can handle the parameters list as it is more convenient, e.g. `table` expects an Enumerable, while `details` expects a single object. :smile: