Separate name from ruby_version attributes to fix #49.

This fixes #49.
My understanding is that `name` does not need `:name_attribute => true` because by default the name will be given an attribute called `name`. Line 24 therefore is a little pedantic and only there for posterity.

I can't find any applicable Chef documents but you can see another example [here](http://neethack.com/2013/10/understand-chef-lwrp-heavy-version/) if you scroll down to "Resource and Provider (Light version – LWRP)"