Allow to pass arguments to shell scripts

[certik]

Compare:

$ zsh ~/bin/conda_activate.sh xx
OK:
xx
$ shell ~/bin/conda_activate.sh xx
error: unexpected argument 'xx' found

Usage: shell [OPTIONS] [FILE]

For more information, try '--help'.

With ~/bin/conda_activate.sh:

$ cat ~/bin/conda_activate.sh
echo "OK:"
echo $1

[wolfv]

I think this is almost the same as supporting functions, right?

[certik]

I think passing arguments to scripts is allowing $1 to work. I don't know if internally that would be the same implementation as implementing functions.

[wolfv]

Implemented something in #232