Cannot uninstall in projects depending on nikic/php-parser

[nclsHart]

In projects depending on nikic/php-parser, phpstan/phpstan-shim cannot be uninstalled.
For example, this issue affect all Symfony projects using symfony/maker-bundle.

Simple way to reproduce:

$ composer req --dev phpstan/phpstan-shim nikic/php-parser
$ composer remove phpstan/phpstan-shim
$ tree vendor
vendor
├── autoload.php
├── bin
│   ├── phpstan -> ../phpstan/phpstan-shim/phpstan
│   └── phpstan.phar -> ../phpstan/phpstan-shim/phpstan.phar
├── composer
└── phpstan
    └── phpstan-shim
        ├── LICENSE
        ├── README.md
        ├── bootstrap.php
        ├── composer.json
        ├── phpstan
        └── phpstan.phar

4 directories, 18 files

Probably related to #29.

[ondrejmirtes]

Should work now, please test dev-master: 10caff5