We need a dev Scala version in _config.yml

[jarrodu]

713e699 introduced a bug that breaks the Development Release link in the footer of all the pages.

We need a value for devscalaversion that points to an actual page. The current rendering gives a link of http://www.scala-lang.org/download/.html.

[SethTisue]

hmm. there's not really anything we can fill in there until 2.13.0-M1 comes out, which won't be for a while (2017 sometime).

I really don't think we need to make the development version that easy to find, so I'd be fine with a PR that simply removed the devscalaversion line and removed the link from the footer.

[SethTisue]

fixed (in a better way) by #539