createClient takes one argument for configuration and returns an instance of the api client. The configuration object can contain the following options:
* `apiKey` string (required) - Your challonge API Key
*`apiKey` string (required) - Your challonge API Key
* `subdomain` string (optional) - Setting the subdomain automatically passes tournament[subdomain] and prefixes the subdomain to tournament urls. If you don't want to pass a subdomain to the constructor, and want to use an organization (or multiple organizations), you must use client.setSubdomain('subdomain') before making api calls.
*`subdomain` string (optional) - Setting the subdomain automatically passes tournament[subdomain] and prefixes the subdomain to tournament urls. If you don't want to pass a subdomain to the constructor, and want to use an organization (or multiple organizations), you must use client.setSubdomain('subdomain') before making api calls.
* `format` string (optional) - The format of the response data. Defaults to 'json'. If set to 'json', will return javascript objects. 'xml' will return the raw text string.
*`format` string (optional) - The format of the response data. Defaults to 'json'. If set to 'json', will return javascript objects. 'xml' will return the raw text string.
