Fix `ambiguous Java methods found` warning for java.util.TreeMap

When running `rake test`, the `find_intersections` method of the `Ruling` class raised `warning: ambiguous Java methods found, using java.util.TreeMap(java.util.Comparator)`. Although the `new` method of `java.util.TreeMap` selects the correct constructor, `TreeMap(Comparator<? super K> comparator)`, this warning was fixed by 'select[ing] a particular constructor by signature use reflection'.

References:
* Constructors
  https://github.com/jruby/jruby/wiki/CallingJavaFromJRuby#constructors
* Class TreeMap<K,V>
  http://docs.oracle.com/javase/8/docs/api/java/util/TreeMap.html