Deployment fails

[foodelevator]

-----> Java app detected
-----> Installing OpenJDK 11...

       !     ERROR: Unsupported Java version: 11

       Please check your system.properties file to ensure the java.runtime.version
       is among the list of supported version on the Dev Center:
       https://devcenter.heroku.com/articles/java-support#supported-java-versions
       You can also remove the system.properties from your repo to install
       the default 1.8 version.
       If you continue to have trouble, you can open a support ticket here:
       https://help.heroku.com

       Thanks,
       Heroku

On the linked page, java 11 seems to still be supported.

[foodelevator]

Fixed by #49