slosh shell tests

[gpwclark]

slosh needs tests for shell like things, i.e.

1. create some random directory hierarchies and text files
2. test different redirect/pipes
3. suspend/kill/job control
   anything to catch a regression we might run into on the shell,

shell-tests/test-simple-redirect.slosh
shell-tests/test-simpe-pipe.losh

etc. and a test runner to test them all.