sbt 1.2.7 -> sbt 1.2.8 (#6)

Dockerfile

@@ -4,7 +4,7 @@
 ARG OPENJDK_TAG=8u181
 FROM openjdk:${OPENJDK_TAG}
 
-ARG SBT_VERSION=1.2.7
+ARG SBT_VERSION=1.2.8
 
 # Install sbt
 RUN \

README.md

@@ -28,7 +28,7 @@ local caches as volumes and set the working directory as well:
 To build, you need to specify the desired openjdk and sbt versions via
 `--build-arg` parameters:
 
-    docker build --build-arg OPENJDK_TAG=8u181 --build-arg SBT_VERSION=1.2.7 .
+    docker build --build-arg OPENJDK_TAG=8u181 --build-arg SBT_VERSION=1.2.8 .
 
 ## Pushing a new tag to DockerHub
 
@@ -42,7 +42,7 @@ Then use the following recipe to build and push:
 
 ```bash
 OPENJDK_TAG=8u181
-SBT_VERSION=1.2.7
+SBT_VERSION=1.2.8
 
 docker build \
     --build-arg OPENJDK_TAG=$OPENJDK_TAG \