Fix type definitions

[gabrielvincent]

This pull request fixes the following type definitions:

~province: string~ -> province: string | null ~province_code: string~ -> province_code: string | null ~latitude: string~ -> latitude: number | null ~longitude string~ -> longitude: number | null

Example of actual data sent by the Shopify API:

province can be null. latitude/longitude are number

latitude/longitude can be null

[coveralls]

Coverage remained the same at 100.0% when pulling 2df1642e8a0ee96629f0bd0ccc73b90923754b55 on gabrielvincent:fix/types into b1e7a9e38120890c47acae21bac8dfd19d9e6cd5 on MONEI:master.

[lpinca]

Thank you.