os.getlogin() in simlib.py fails and the possible solution

Running make_simlibs.py leads to the following error:
```
File "/home/andersonlai/anaconda3/lib/python3.7/site-packages/opsimsummary/simlib.
py", line 111, in get_simlibVars
    user = os.getlogin()
FileNotFoundError: [Errno 2] No such file or directory
```
change it 
```getpass.getuser()``` may work (need to ```import getpass```)