Zoltan 3.8 (new formula): Library for graph partitioning and load balancing

This request is for the latest version of Zoltan (Web site: http://www.cs.sandia.gov/Zoltan).
This formula passes `brew audit zoltan` without errors.

It has several optional dependencies: Scotch, ParMETIS, and Fortran (Scotch and ParMETIS is in homebrew-science).
Zoltan optionally supports [PaToH](http://www.cs.bilkent.edu.tr/~aykanat/pargrp/patoh/) library but I did not make a dependency for it because it is not in homebrew-science and other taps.

Note: There was another pull request for Zoltan 3.3 (Homebrew/homebrew#7582) but it was closed.