I am creating a new theme from scratch for magento 2, I have created the necessary files for it. but when i open the admin pannel it gives error, and the error log show the following error "Theme's key does not correspond to required format"

my theme.xml code:

```
<theme xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Config/etc/theme.xsd">
 <title>WPIINC</title> <!-- your theme's name -->
 <media>
     <preview_image>media/preview.jpg</preview_image> <!-- the path to your theme's preview image -->
 </media>
</theme>

```

composer.json code:

```
{
"name": "wpiinc/wpiinc",
"description": "N/A",
"require": {
    "php": "~5.5.0|~5.6.0|~7.0.0",
    "magento/theme-frontend-blank": "100.0.*",
    "magento/framework": "100.0.*"
},
"type": "magento2-theme",
"version": "100.0.1",
"license": [
    "OSL-3.0",
    "AFL-3.0"
],
"autoload": {
    "files": [
        "registration.php"
    ]
}
}

```

registration.php code:

```
<?php
/**
* Copyright © 2015 Magento. All rights reserved.
* See COPYING.txt for license details.
*/
\Magento\Framework\Component\ComponentRegistrar::register(
\Magento\Framework\Component\ComponentRegistrar::THEME,
'wpiinc/wpiinc',
__DIR__
);

```

folder structure is app->design->frontend->wpiinc->wpiinc

how can i solve this error?
when i run `php bin/magento setup:static-content:deploy` this command i get following error in cmd prompt
"Theme's key does not correspond to required format 'area/vendor/name'"

Please help