Set the process title for more informative ps output

Example:

    turnip@mercutio:~/Code/spring/test/apps/rails-3-2:master$ ps ax | grep spring
    23551 pts/3    Sl     0:00 spring server | rails-3-2 | started 2013-02-01 19:59:57 +0000
    23554 pts/3    Sl     0:01 spring app    | rails-3-2 | started 2013-02-01 19:59:57 +0000 | test mode
    23625 pts/3    Sl     0:00 spring app    | rails-3-2 | started 2013-02-01 20:00:01 +0000 | development mode
remove obsolete comment
Server should terminate its children at exit

Closes #40
Update the walkthrough in the README
Make the test command capable of running directories

This makes it a lot more useful for not much effort, so seems worth it.