bump Scala versions and modernize Travis-CI config

Author: SethTisue

.travis.yml

@@ -1,23 +1,16 @@
-dist: bionic
-
+version: ~> 1.0 # needed for imports
+import: scala/scala-dev:travis/default.yml
 language: scala
+
 scala:
-   - 2.12.12
+   - 2.12.13
    - 2.11.12
-   - 2.13.3
+   - 2.13.4
 
-jdk:
-  - oraclejdk11
-  - openjdk8
-  - openjdk11
+env:
+  - ADOPTOPENJDK=8
+  - ADOPTOPENJDK=11
 
 script:
 - sbt "++ ${TRAVIS_SCALA_VERSION}!" test
 - git diff --exit-code # check scalariform
-
-cache:
-  directories:
-  - $HOME/.m2
-  - $HOME/.ivy2/cache
-  - $HOME/.sbt/boot/
-

project/Dependencies.scala

@@ -3,8 +3,8 @@ import sbt._
 object Version {
   val logback   = "1.2.3"
   val mockito   = "1.16.23"
-  val scala     = "2.13.1"
-  val crossScala = List(scala, "2.11.12", "2.12.12")
+  val scala     = "2.13.4"
+  val crossScala = List(scala, "2.11.12", "2.12.13")
   val scalaTest = "3.2.3"
   val slf4j     = "1.7.30"
 }