Update helpers.py

[nikobenho]

Added out_dir parameter to the functions simple_tpl_from_pars, simple_ins_from_obs and pst_from_parnames_obsnames to allow files to be created in directories other than from where the functions are called. This can be useful if the model files are located in a different directory from the notebook where function calls are made.

I ran pytest --basetemp=runner -n auto autotest/utils_tests.py::pst_from_parnames_obsnames_test which yielded the same result before and after the changes:

utils_tests.py::pst_from_parnames_obsnames_test
  C:\Users\ni6304be\AppData\Local\anaconda3\envs\pyemu_test\Lib\site-packages\pyemu\pst\pst_utils.py:914: UserWarning: error processing instruction file model.output.ins, trying inschek: output file 'model.output' not found

Not sure if that is an error on my part. I'm not a very experienced programmer, just thought I'd try and make a small contribution to make these functions a bit more convenient based on a recent use-case.

Cheers

[coveralls]

coverage: 79.26% (+0.07%) from 79.193% when pulling b041af9 on nikobenho:develop into 3322178 on pypest:develop.