Merge pull request #42 from cb372/scala-2.13.4

Cross-build for Scala 2.13.4

Author: cb372

.travis.yml

@@ -10,6 +10,7 @@ scala:
   - 2.13.1
   - 2.13.2
   - 2.13.3
+  - 2.13.4
 jdk:
   - openjdk8
   - openjdk12

docs/README.md

@@ -94,7 +94,7 @@ The plugin is published for the following Scala versions:
 
 * 2.11.12
 * 2.12.{8, 9, 10, 11, 12}
-* 2.13.{0, 1, 2, 3}
+* 2.13.{0, 1, 2, 3, 4}
 
 ## Changing the log level