Add ... argument to fspe function to pass parameters to functions like psych::fa() and GPArotate::GPFoblq()

[LizHareDogs]

Hi! This is a great package!

I ran into an error from GPFoblq saying that it didn't converge during the default number of iterations. I wanted to be able to set maxiter to a higher number. Adding ... as a parameter to fspe() would allow the user to pass parameters to the inner functions.

I was able to add the ... and avoid the warning, so I'll put in a PR.

Thanks for a relevant and helpful package!

[jmbh]

Hi LizHareDogs,

Yes good point, it should be possible to hand down argument to fa().

Best,
Jonas