Estimators don't have n_iter_ parameter

[stsievert]

Scikit-learn estimators have a n_iter_ parameter. Dask-GLM doesn't.

For example, the Scikit-Learn logistic regression implementation has the n_iter_ parameter (docs). However, the Dask-GLM implementation doesn't (docs).

This issue presented itself in dask/dask-blog#15 (comment)