Improving vertx-heroku example

[Tobias-Doerner]

The current vertx-heroku example is not compiling with Java 10. sun.misc.BASE64Encoder is missing updating the heroku-maven-plugin to the current version fixes that issue. I also would like to propose to use the vertx config retriever for fetching the system properties and the config vars defined in heroku's application settings.

[vietj]

what is using sun.misc.BASE64Encoder ?

[Tobias-Doerner]

heroku-maven-plugin version 0.5.6 is using sun.misc.BASE64Encoder, look here https://github.com/heroku/heroku-maven-plugin/blob/heroku-sdk-parent-0.5.6/heroku-deploy/src/main/java/com/heroku/sdk/deploy/Deployer.java