Making the StarCluster class more consistent with existing clustering classes

[josephius]

I noticed that the hyperparameters are currently placed as arguments to the fit function. This is problematic because fit is normally called without arguments, and the arguments are instead passed to the constructor method when the class object is initialized.

If there are no objections I'm going to make changes accordingly. This may break any code that passes arguments to the fit function, but is probably needed before I can make the predict function work properly.