expand path when loading java ext to make it load from within a jar file

If you try to bundle a jruby app+gems in a jar file and run it without exploding it, the extension can not be loaded. The user facing exception is "NameError: cannot load Java class org.bson.types.ObjectId" but the underlying problem is the following:

LoadError: no such file to load -- file:/Users/andi/src/tik/mediaservice2/target/mediaservice-0.0.1-SNAPSHOT.jar!/ruby/jruby/1.9/gems/bson-1.9.2-java/lib/bson/../../ext/jbson/lib/java-bson
  require at org/jruby/RubyKernel.java:1085
   (root) at file:/Users/andi/src/tik/mediaservice2/target/mediaservice-0.0.1-SNAPSHOT.jar!/ruby/jruby/1.9/gems/bson-1.9.2-java/lib/bson/bson_java.rb:20
  require at org/jruby/RubyKernel.java:1085
   (root) at file:/Users/andi/src/tik/mediaservice2/target/mediaservice-0.0.1-SNAPSHOT.jar!/ruby/jruby/1.9/gems/bson-1.9.2-java/lib/bson.rb:1
[...]

Using expand_path to eliminate the ../.. in the path fixes the error