Added missing language attribute.

Author: milessabin

_sips/sips/2017-11-20-byname-implicits.md

@@ -141,7 +141,7 @@ trait Semigroup[A] {
 
 If we have instances for basic types,
 
-```
+```scala
 object Semigroup {
   implicit val intSemigroup: Semigroup[Int] =
     new Semigroup[Int] {
@@ -163,7 +163,7 @@ object Semigroup {
 then we can manually write instances for, for example, tuples of types which have `Semigroup`
 instances,
 
-```
+```scala
 implicit def tuple2Semigroup[A, B]
   (implicit
     sa: Semigroup[A],