DepResolver

This is the `depresolve` implementation.

The depresolve just includes the direct dependencies, I should include the indirect ones?

PTAL to the output:
```json
[
    {
        "Raw": "nikic/php-parser",
        "Target": {
            "ToRepoCloneURL": "https://github.com/mcuadros/php-parser.git",
            "ToUnit": "nikic/php-parser",
            "ToUnitType": "ComposerPackage",
            "ToVersionString": "dev-position",
            "ToRevSpec": "256df7d155ce367acc4a2b3e423f7fc77523ebc8"
        }
    },
    {
        "Raw": "symfony/console",
        "Target": {
            "ToRepoCloneURL": "https://github.com/symfony/console.git",
            "ToUnit": "symfony/console",
            "ToUnitType": "ComposerPackage",
            "ToVersionString": "2.5.*",
            "ToRevSpec": "61b13c27c9258e97009249d4ef193c964bf346b7"
        }
    },
    {
        "Raw": "phpunit/phpunit",
        "Target": {
            "ToRepoCloneURL": "https://github.com/sebastianbergmann/phpunit.git",
            "ToUnit": "phpunit/phpunit",
            "ToUnitType": "ComposerPackage",
            "ToVersionString": "4.3.*",
            "ToRevSpec": "2dab9d593997db4abcf58d0daf798eb4e9cecfe1"
        }
    }
]
```

The toolchain now is running, with many pending things, but is working.