Decode returned JSON into PHP object

Decode JSON to allow PHP to use the object immediately.

IE:
$customer = $this->stripe->customer_create( $vars, … );
echo $customer->id;
Added currency to config

Default set to 'usd'
Revert "Decode returned JSON into PHP object"

This reverts commit d04c6406e1ee1ea35bca06759976a007d10bbd27.
Merge pull request #2 from daverogers/master

add currency config value