Shopifyapi

- Package bug fix

- Removed support for legacy auth
- Updated to pyactiveresource v2.0.0 which changes the default form to JSON
- in Session::request_token params is no longer optional, you must pass all the params
and the method will now extract the code
- made create_permission_url an instance method, you'll need an instance
of session to call this method from now on
- Updated session.request_token
- Updated Session to better match the ShopifyAPI Ruby gem
- Updated the readme to better describe how to use the library
- Added support for CustomerSavedSearch (CustomerGroup is deprecated)

- Fix thread local headers to store a copy of the default hash which
prevents activate_session in one thread from affecting other threads.

- Fix deserializing and serializing fulfillments which can now contain
arrays of strings in the tracking_urls attribute.

- Fix parameter passing for order cancellation.
- Fix Product.price_range method for variants with different prices.

- Fixed another bug in Image size methods regex.