Incompatibility with Java 9 - JRE Path changed

PyJnius looks for the path 

`/Library/Java/JavaVirtualMachines/jdk-9.jdk/Contents/Home/jre/lib/server/libjvm.dylib`

but the `jre` folder doesn't exist in this hierarchy anymore and it should look for

`/Library/Java/JavaVirtualMachines/jdk-9.jdk/Contents/Home/lib/server/libjvm.dylib`