Add installation files for composer and modman tools

You could also add new installation procedures in the README file 

#### Using modman

Install module using [modman](https://github.com/colinmollenhour/modman):

        modman clone git://github.com/GMaissa/magecache.git


#### Using composer

Install module using [composer](https://getcomposer.org/) and [magento-composer-installer](https://github.com/magento-hackathon/magento-composer-installer):

1. Add the requirements in your composer.json file :

        {
            "require": {
                "magento-hackathon/magento-composer-installer":"*",
                "smile-sa/magecache": "*"
            },
            "repositories": [
                {
                    "type": "vcs",
                    "url": "https://github.com/magento-hackathon/magento-composer-installer"
                },
                {
                    "type": "vcs",
                    "url": "https://github.com/Smile-SA/magecache"
                }
            ],
        }

2. Install all dependencies:

        curl http://getcomposer.org/installer | php
        php composer.phar install