Include 'all' as a field attribute of ManyToMany relationships.

[YPCrumble]

Thanks for maintaining this great repo! This is really an issue, but the fix is easy so thought it better to post as a PR. If I've missed something feel free to close.

Per the docs It's possible to call all() on a many to many attribute. For example, the docs call a1.publications.all() in their example.

I'm seeing this error pop up which I don't believe is a configuration error.

[atodorov]

Change looks good but you need to add the tests for it as well.

[coveralls]

Pull Request Test Coverage Report for Build 1382

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-86.9%) to 0.0%

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Totals
Change from base Build 1349:	-86.9%
Covered Lines:	0
Relevant Lines:	0

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💛 - Coveralls

[YPCrumble]

@atodorov thank you! Added the test - I believe this is correct but let me know if it's not? Also added to the CHANGELOG for release today but happy to remove or edit that if you'd prefer.

[YPCrumble]

@atodorov I'm actually going to close this for now - I'm not 100% sure it's necessary as this is actually an issue with my factories, not a plain Django model.