Why doesn't composer update yii2?

Question

Yii

Task: upgrade yii2 core from 2.0.0-rc to version 2.0.0. But when I write "composer update" I get "Nothing to install or update". The vendor yii2 folder contains version 2.0.0-rc. Why is it not updated?
UPD.: even when I delete composer.lock and do composer install, it still says "Nothing to install or update"...
composer.json:

{
    "name": "yiisoft/yii2-app-basic",
    "description": "Yii 2 Basic Application Template",
    "keywords": ["yii2", "framework", "basic", "application template"],
    "homepage": "http://www.yiiframework.com/",
    "type": "project",
    "license": "BSD-3-Clause",
    "support": {
        "issues": "https://github.com/yiisoft/yii2/issues?state=open",
        "forum": "http://www.yiiframework.com/forum/",
        "wiki": "http://www.yiiframework.com/wiki/",
        "irc": "irc://irc.freenode.net/yii",
        "source": "https://github.com/yiisoft/yii2"
    },
    "minimum-stability": "dev",
    "require": {
        "php": ">=5.4.0",
        "yiisoft/yii2": "*",
        "yiisoft/yii2-bootstrap": "*",
        "yiisoft/yii2-swiftmailer": "*",
  "mgargano/simplehtmldom": "dev-master"
    },
    "require-dev": {
        "yiisoft/yii2-codeception": "*",
        "yiisoft/yii2-debug": "*",
        "yiisoft/yii2-gii": "*"
    },
    "suggest": {
        "codeception/codeception": "Codeception, 2.0.* is currently works well with Yii.",
        "codeception/specify": "BDD style code blocks for PHPUnit and Codeception",
        "codeception/verify": "BDD Assertions for PHPUnit and Codeception"
    },
    "scripts": {
        "post-create-project-cmd": [
            "yii\\composer\\Installer::setPermission",
            "yii\\composer\\Installer::generateCookieValidationKey"
        ]
    },
    "config": {
        "process-timeout": 1800
    },
    "extra": {
        "writable": [
            "runtime",
            "web/assets"
        ],
  "asset-installer-paths": {
            "npm-asset-library": "vendor/npm",
            "bower-asset-library": "vendor/bower"
        },
        "executable": [
            "yii"
        ],
        "config": [
            "config/web.php"
        ]
    }
}

Answer 1

Want the latest stable - *@stable. Want the latest unstable - * @dev (most likely will refer to the latest commit in master).
You set the version, do a composer update and wait... And then see if there are any conflicts.

Answer 2

Delete the composer.lock file , it fixes the version at the time of installation and then uses it.

Answer 3

Try like this

"require": {
   "yiisoft/yii2": "2.0.*@stable",
...
}

Answer 4

Delete composer.lock and vendor folder .
Then run composer install

Answer 5

If the config is correct, just delete the vendor folder and update...