fix for writing uzt with iet != 0 and unit handling (#377)
fix for writing uzt with iet != 0 and unit handling (#377)

* fix for tkstp >9999

* uzf1 load fix for nwt models with 'options'

* bit more descriptive in test

* another fix for uzf1 load with 'nwt_11_fmt'

* revert uzf1 so can easily identify new changes

* another fix for uzf1 load with 'nwt_11_fmt'

* docstring-ing

* bug fix when writing uzt with iet and use reservedunit

* add to docstring

* use defaultunit

jentjr/flopy,jentjr/flopy,aleaf/flopy,aleaf/flopy