superficial reorg of imports

Signed-off-by: mark hellewell <mark.hellewell@icloud.com>
removed clint dependency, use stdlib argparse, YEAH!

cleaner building of requirements dicts

moved code to a main function

started test suite

added notes

removed unused import and fixed syntax error

fixed typo

updated readme
output notices regarding rotten reqs to stderr

this is part of a longer term goal to make piprot more useful as a cron job or similar
Merge pull request #15 from markhellewell/master

removed need for clint, tidied argument parsing, added multi-file support, rotten reqs to STDERR