Allow passing additional data to 3DS2 complete method (#32)

fix a docblock example and some types

Allow changing spreedly base url in config (#31)

enhance readme, add package.json for installing and running tests

Make sure capture currency does not default to USD (#29)

add ability to complete 3DS 2 transaction, closes #28

Make Spreedly::client() public so we can access the raw Guzzle interf…

…ace for calls this library doesn't natively support (#27)

always return array or string instead of void (#26)