modularize nan value conversion
modularize nan value conversion

extract from read_data_objects; make a stand alone function convert_nans; do convert_nans inside of read_model_data_from_csv

probcomp/crosscat,mit-probabilistic-computing-project/crosscat,fivejjs/crosscat,probcomp/crosscat,probcomp/crosscat,probcomp/crosscat,probcomp/crosscat,fivejjs/crosscat,probcomp/crosscat,mit-probabilistic-computing-project/crosscat,fivejjs/crosscat,fivejjs/crosscat,fivejjs/crosscat,fivejjs/crosscat,mit-probabilistic-computing-project/crosscat,mit-probabilistic-computing-project/crosscat,mit-probabilistic-computing-project/crosscat,probcomp/crosscat,fivejjs/crosscat,mit-probabilistic-computing-project/crosscat,mit-probabilistic-computing-project/crosscat,probcomp/crosscat