install incorrect on Windows

When installing the gem, it does not copy the executable into ruby/bin, nor does it create a bat file. 
I manually copied the executable into ruby bin

```
copy C:\Ruby200\lib\ruby\gems\2.0.0\gems\ru-0.1.4\bin C:\Ruby200\bin
```

I needed to change the line

> require_relative '../lib/ru'

to

> require 'ru'

Are you doing something clever with where you expect the executable to be?
