improve `step2` command line feedback

If I call step2 manually, it reports back that I shouldn't do that. But why not? At least make there be some feedback that explains how to call it, or how the arguments are parsed.

this is how useless it currently is:

integral:~ ofloveandhate$ step2
Insufficient, incorrect, or unparseable arguments... 
step2 is intended to be automatically called from paramotopy...

or, asking for help the usual way,

integral:~ ofloveandhate$ step2 -h
Insufficient, incorrect, or unparseable arguments... 
step2 is intended to be automatically called from paramotopy...
integral:~ ofloveandhate$ 

there's clear room for improvement here.