Build docker image

##$ ./gradlew buildDocker --- Error
$ ./gradlew buildImage
$ docker images
REPOSITORY                      TAG                 IMAGE ID            CREATED              SIZE
ryanmckay/java-docker-example   latest              4bd58fcbb0b4        About a minute ago   115MB

Run

$ docker run -p 8080:8080 -d ryanmckay/java-docker-example
$ curl localhost:8080/greeting