Adds better handling for dotted notation fields in is_expanded

[Caiofcas]

Basically implements the proposed behaviour in #48 with some small tweaks:

• utilizes WILDCARD_VALUES instead of hardcoding "~all"
• receives a request as the argument
• converts tests from pytest notation to django notation

Most of the credit to @mitchelljkotler for actually implementing the solution

[Caiofcas]

Ping @rsinger86

[dest81]

Any progress here?
@Caiofcas thanks for working on this.
I would suggest to add check if expand_value is not None:

    if not expand_value:
        return False