code: public static Version min(Version v1, Version v2) {
          require(v1 != null, "v1 is null");
          require(v2 != null, "v2 is null");
          return compare(v1, v2, false) <= 0
                  ? v1
                  : v2;
      }
docs: Returns the lower of the two given versions by comparing them using their natural
  ordering. If both versions are equal, then the first argument is returned.
  
  @param v1 The first version.
  @param v2 The second version.
  @return The lower version.
  @throws IllegalArgumentException If either argument is <code>null</code>.
  @since 0.4.0