Correct composer.json

Corrects naming convention, autoload definition and removes unnecessary properties.

'type' and 'repositories' are unnecessary. 'autoload' should use class map instead of PSR-0. The library doesn't follow PSR-0, instead you will want a class map.

Instead of 'version', please use tags. Using tags allows us to actually use this repo with ease, and removes human-error factor. Tags bring working version constraints and dist support (which removes git dependency when using Composer).