Merge pull request #144 from SethTisue/scala-3.0.0-M2

bump Scala versions (to 2.13.4 and 3.0.0-M2)

Author: SethTisue

.travis.yml

@@ -5,8 +5,8 @@ import: scala/scala-dev:travis/default.yml
 language: scala
 
 scala:
-  - 2.13.3
-  - 3.0.0-M1
+  - 2.13.4
+  - 3.0.0-M2
 
 env:
   - ADOPTOPENJDK=8