include setup script

[hughrun]

Maybe a Bash file, but it ideally needs to run pocket_tools.authorise, do a first pass of stash and lucky_dip, and set up the cron job or launchd file.

[hughrun]

This can be done in Python.

• make main.py executable and symlink to /usr/local/bin/pocketsnack
• run pocketsnack authorise
• optionally run pocketsnack schedule (to set up the regular job using launchd)

This will require an update to the README as pocketsnack becomes an executable.