Support for new options:
 - additionalParams
 - additionalAuthorizeParams
 - additionalLogoutParams
Simple documentation for the new options:
 - additionalParams
 - additionalAuthorizeParams
 - additionalLogoutParams
Fixed variable name.
Fixed all the linter warnings.
Added 'getAdditionalParams' unit tests.
Merge pull request #63 from tkopczuk/additional-query-params

Ability to add additional query parameters in authorize, logout or all requests. This PR fixes #57.