Minor wording change
Split Puppet docs to make 3.5 a new version

The original plan of breaking on major versions no longer makes the sense we
thought it would: we've been more parsimonious with major versions than we
thought, and have made many significant changes in minor versions.
Remove old planning garbage from puppet 3.5 sidebar

We can get it from the puppet 3 one if needed.
Collapse conditional descriptions of things that are old news in 3.5