[feature] Add support for customer search and customer group search.
[feature] Add support for customer search and customer group search.

Shopify/shopify_python_api,SmileyJames/shopify_python_api,varesa/shopify_python_api,metric-collective/shopify_python_api,asiviero/shopify_python_api,ifnull/shopify_python_api,gavinballard/shopify_python_api