Add posability for dynamic configuration

[NikolayMurha]

Usage:

use SEOstats\Config\ApiKeys;

ApiKeys::configure([
    'MOZSCAPE_ACCESS_ID' => '<MOZSCAPE ACCESS ID>',
    'MOZSCAPE_SECRET_KEY' => '<MOZSCAPE SECRET KEY>',
]);

Or:

ApiKeys::set('MOZSCAPE_ACCESS_ID', '<MOZSCAPE ACCESS ID>');
ApiKeys::set('MOZSCAPE_SECRET_KEY', '<MOZSCAPE SECRET KEY>');

[prionkor]

+1 Not only api keys but also other configuration settings too. For example setting user-agent, proxy or other curl parameters.