Add screensaver watcher and invoker scripts

xscreensaver-watcher.py cares only about stdin, and can be tested by
piping the contents of the fixtures to its stdin:

    python xscreensaver-watcher.py < fixtures/lock-example.txt

The clementine-screensaver-watcher.sh script is meant to be invoked when
I first log in to my login session, and pipes the output of
xscreensaver-command to our python script:

    xscreensaver-command -watch | python xscreensaver-watcher.py
Updated invocation helper script

Assumes that this script and the python script are symlinked in ~/bin/
pep8 fixes
Merge pull request #1 from gknoy/initial-script

Initial script