Help text prints invalid usage

`map --help` produces the following:

```
...
map <argname> <command>... --separator <separator>
...
```

This is incorrect and doesn't work. The separator flag needs to come before other arguments.

`echo hay hey | map ,, echo ,, ,, -s " "` prints `hay hey hay hey -s`.

A correct invocation would actually be `echo hay hey | map -s " " ,, echo ,, ,, `.