export module as window.R rather than window.ramda

This has been discussed in the past. I believe it's a good idea.

This will break backwards compatibility. Those who which to update without doing a find and replace can define their own alias:

```html
<script src="path/to/ramda.js"></script>
<script>window.ramda = window.R</script>
<script src="path/to/myapp.js"></script>
```