bump Scala version to 2.12.0

ha, wow, pretty embarrassing this got missed for the entire 2.11.x
cycle

Author: SethTisue

_config.yml

@@ -15,7 +15,7 @@ keywords:
 - Document
 - Guide
 
-scala-version: 2.10.0
+scala-version: 2.12.0
 
 highlighter: rouge
 permalink: /:categories/:title.html