Enforce the use of builders in Ruby and Chef statements

Enforce the use of builders in Ruby and Chef statements, as proposed [here](https://github.com/jclouds/jclouds-examples/pull/27/files#r3608314).

Once this has been merged, the [corresponding changes in jclouds-chef](https://github.com/nacx/jclouds-chef/commit/b0302109484c4fbf8b49e908837fa3b44761a622) should be merged too.

/cc @everett-toews