Kohana 3.1 Zip module

This module is based off the one found in CodeIgniter 2.0.2.
It comes with an example controller /koziptest and 2 example files for zipping.

Documentation can be found here:
http://codeigniter.com/user_guide/libraries/zip.html

Additions made by me include:
- Chainable methods. read_file, read_dir and read_archive now throw Exceptions on error
- 'download' method now takes a Request as its first parameter.

For more information see:
http://www.flynsarmy.com/2011/06/download-multiple-files-with-kohana-3-1-zip-library