Scala 2.11.0-M4

Added the news item and download page for 2.11.0-M4. Review by @heathermiller, please.

I verified it looks ok in jekyll (btw, on jekyll 1.1.2, the command to start the server is `jekyll serve`).

I'd also suggest switching to github flavored markdown in _config.yml:
```
--- i/_config.yml
+++ w/_config.yml
@@ -5,3 +5,6 @@ devscalaversion: "2.11.0-M4"
 scala_maindownload_unix: "/files/archive/scala-2.10.2.tgz"
 scala_maindownload_windows: "/files/archive/scala-2.10.2.msi"
 baseurl: ""
+markdown: redcarpet
+redcarpet:
+  extensions: ["no_intra_emphasis", "fenced_code_blocks", "autolink", "tables", "with_toc_data"]
```