allow non-tuple data in the new train! (#2119)
* allow non-tuple data
* cl/batchme
* add tests
* test multiple callback
* cleanup notes
* cleanup
* cleanup
* remove callbacks
* cleanup
* Update src/train.jl
Co-authored-by: Kyle Daruwalla <daruwalla@wisc.edu>
Co-authored-by: Kyle Daruwalla <daruwalla@wisc.edu>
