Scala 2.10.4-RC1

Generated with:

```
hub clone scala/make-release-notes
cd make-release-notes
git checkout 2.10.x

sbt -Dfile.encoding=UTF-8 console

scala> MakeReleaseNotes.genPR("2.10.3", "2.10.4-RC1", "2013/12/20")
ctrl-D ctrl-D

cp 2013-12-20-2.10.4-RC1.md ../scala-lang/download/_posts/
cp 2013-12-20-release-notes-2.10.4-RC1.md ../scala-lang/news/_posts/
```