Add timeout option for HTTP requests.

Consider array structure when building a query string The array elements are separated by comma.

Set data in caller.

Select PostCaller on `:post` method.

use readable constants for HTTP-response type In order to decide how the HTTP response of a Hets::Caller should be served, we'll use speaking constant names.

perform proposed hound-style fixes.

adjust parsing to work with io/tempfile instance In order for the API-system to work properly we'll need to work with the streamed Tempfile. So instead of working with filepaths we'll need to pass io-instances to parsing-processes.

add basic classes to call hets-api.