[zaphod-v0.4][issue-034]: Fix errors in demo.txt

FEATURE
issue-034-fix-errors-in-demo-txt

SYNOPSIS
[modified]doc/demo.txt: Fix inconsistencies and errors in the demo walkthrough.

DETAILS
Fix errors and inconsistencies in the demo walk through. Most of the fixes
are to adhere to the convention that explationtions are placed on lines
starting with hashes and output from a command is indented two spaces.
Some logical errors and typos were also fixed.