extension for glmer models

Hi Dr. van Buuren,

I'm a statistician at Stanford University in the US; I am trying out your imputation software, and I was having trouble getting pool() to work with a mixed-effects logistic model. I can provide the relevant data and code if helpful. I made three small edits that removed the error I was getting.

I also added a metadata file to enable the project to be opened in the Eclipse plugin for R (StatET), and .gitignored a .pdf file that got generated when I built the package.

I hope my edits to pool.r are correct; let me know if you would like any more information about what I was trying to do.
 
Many thanks,
Doug