osm2po 4.8.8 (new formula)

I am having a similar issue to

https://github.com/Homebrew/homebrew/issues/27340#issuecomment-42640774

trying to install osm2po.  I'm not much of a programmer but need the routing functionality.  I tried this approach and I am getting an error I don't understand.  The whole program is a simple jar file, although I don't know much about that either.  Here is an example of how it is used.  

http://anitagraser.com/2011/12/15/an-osm2po-quickstart/

Particularly, you just download, unzip and call from where you extracted it.  Here is my formula

```ruby
require "formula"
class Osm2po < Formula
  homepage "osm2po.de/"
  url "http://osm2po.de/download.php?lnk=osm2po-4.8.8.zip"
  sha1 "878384eabbdfe4d9dfec6f354239db83ba7c25e1"
 def install
    libexec.install Dir["*"]
    ["gcl", "gclc"].each {|b| (bin/b).write_env_script libexec/b, "GACELA_PATH" => libexec, "CLASSPATH" => "$CLASSPATH:#{libexec}"}
  end
end 
```
I changed the name, as before the formula was automatically named "download.php?lnk=osm2po-4.8.8.zip".  When I run brew install osm2po it gives me the following error in the terminal

```ssh
Bluebirds-MacBook-Pro:~ bluebird$ brew install osm2po
==> Downloading http://osm2po.de/download.php?lnk=osm2po-4.8.8.zip
######################################################################## 100.0%
[/Library/Caches/Homebrew/osm2po-4.8.8.zip]
  End-of-central-directory signature not found.  Either this file is not
  a zipfile, or it constitutes one disk of a multi-part archive.  In the
  latter case the central directory and zipfile comment will be found on
  the last disk(s) of this archive.
unzip:  cannot find zipfile directory in one of /Library/Caches/Homebrew/osm2po-4.8.8.zip or
        /Library/Caches/Homebrew/osm2po-4.8.8.zip.zip, and cannot find /Library/Caches/Homebrew/osm2po-4.8.8.zip.ZIP, period.
Error: Failure while executing: unzip -qq /Library/Caches/Homebrew/osm2po-4.8.8.zip 
```
I have checked my computer and the file is there and the name is correct.  I have also unzipped it to check what is inside and the following files are there:
- demo.bat
- demo.sh
- osm2po_core-4.8.8-signed.jar
- [folder]osm2po-doc
- [folder]osm2po-plugins
- osm2po.config

This is my first formula, so any help would be greatly appreciated.  With the functionality of this program, all open source GIS users will appreciate having this available.  Thanks