Adding classmap for composer.json

Commit e5d85eabb4ea6e6b773bb8bdf5d5cc178348e531 broke autoloading feature for composer modules.
This patch tries to fix that.

PS. As this is the official @Infusionsfot PHP API and some companies rely on this project, please consider using some additional QA step before pushing code into the master repository and using [tags](http://getcomposer.org/doc/04-schema.md#version) as a versioning for composer module so we can lock the dependencies on particular version.