Added composer.json file to 2.7 version

[dmouse]

This is an example to how to looks the composer file in the Elis project.

The users can be install Elis using the composer command

Install

$ composer install remotelearner/eliscore:2.7

Update

$ composer update remotelearner/eliscore

This repo only need create a alias tag for each branch, MOODLE_27_STABLE -> 2.7, more info in https://getcomposer.org/doc/04-schema.md#version