Cleanup composer structure

Cleaned up composer structure, removed composer.phar file and added to ignore (the actual phar should never be committed, especially since it will be ignored when installed as a library), refactored tests mildly to not rely on PSR-0 autoloading in composer.json, added phpunit to the require-dev dependencies.

**Note:** this is identical to the process taken with my other pull request at cowlby/monologgly#1