mkremer/nil_object — pull request #1 by satoship (2013-05-02 03:30:48+00:00)
Title: add NilObject#to_str

I want to use `String(NilObject.new)` (which is called by csv library in ruby 1.9 or more). But this raises error.

```
TypeError: can't convert NilObject to String (NilObject#to_str gives NilObject)
```