How can I set configuration values in Magento 2?

This seems to work:

class InstallData implements InstallDataInterface 
{
    public function __construct(
        LoggerInterface $loggerInterface,
        \Magento\Framework\App\Config\ConfigResource\ConfigInterface  $resourceConfig)
    {
        $this->logger = $loggerInterface;
        $this->resourceConfig = $resourceConfig;
    }        

    public function install(ModuleDataSetupInterface $setup, ModuleContextInterface $context)
    {
        $setup->startSetup();

        $this->resourceConfig->saveConfig(
            'a/b/c', 
            'value', 
            \Magento\Framework\App\Config\ScopeConfigInterface::SCOPE_TYPE_DEFAULT, 
            \Magento\Store\Model\Store::DEFAULT_STORE_ID
        );

        $setup->endSetup();
    }   
}

The following interface can be used \Magento\Framework\App\Config\Storage\WriterInterface, it has 2 methods:

• save($path, $value, $scope = ScopeConfigInterface::SCOPE_TYPE_DEFAULT, $scopeId = 0)
• delete($path, $scope = ScopeConfigInterface::SCOPE_TYPE_DEFAULT, $scopeId = 0)

It is more high-level compared to \Magento\Config\Model\ResourceModel\Config, and should be used from client code.