Upgrade tot Scala 2.11.0-M5

review by @gkossakowski, /cc @jsuereth

note the 
```diff
+// scalap depends on scala-compiler, which depends (for the scaladoc part) on scala-xml and scala-parser-combinators
+// more precisely, scala-compiler_2.11.0-M5 depends on
+//                      scala-xml_2.11.0-M4 and
+//       scala-parser-combinators_2.11.0-M4,
+// so that we get a binary version incompatibility warning
+// it isn't really a problem, but we should consider doing something about this
+// my preference: modularize scaladoc
+conflictWarning ~= { _.copy(failOnConflict = false) }
```