Scatter blocks can now receive external input
Replace compress(1) with xz
Add compress-compare test case
Word-properties example now reads stdin
Correct handling of piped input

- Use of <&3 in sgsh-tee invocation allows us to pipe into the
  command, although it is running in the background.
- Grouping commands with { } and specifying their input at the end of the
  group, allows the command sequences to be complex, rather than just
  simple commands.