fix(distributions.conjugate): support total_count_max in DirichletMultinomial distribution

[brendancooley]

Follow on to #1557 for the DirichletMultinomial case.

Prior to this change, users may encounter the error ValueError("Please specify total_count_max in Multinomial distribution.") (see multinomial in distributions.util) when using the distribution inside of traced environments and lack recourse to address the problem.

[brendancooley]

Looks like we're encountering the same CI failure as in #2015 #2015 (comment)

[fehiepsi]

Could you mark this test as xfail in CI instead? like in https://github.com/pyro-ppl/numpyro/blob/master/test/test_examples.py#L52-L59

[brendancooley]

Could you mark this test as xfail in CI instead? like in https://github.com/pyro-ppl/numpyro/blob/master/test/test_examples.py#L52-L59

Absolutely. Done.

[fehiepsi]

Thanks @brendancooley! Could you remove committed png and graph files?

[brendancooley]

Thanks @brendancooley! Could you remove committed png and graph files?

yeesh yes of course. added *.png to the gitignore for future.

[juanitorduz]

We might want to add png as part of the docs right https://github.com/pyro-ppl/numpyro/tree/master/docs/source/_static/img/examples ?

[fehiepsi]

yes, thanks!

[brendancooley]

Happy to put up a PR to revert the change...or maybe try and manage artifact generation during the tests a bit better so that these files don't end up polluting the root directory. Did I miss something in the contributor notes on existing ways to manage this?