port teuthology-ls to use docopt instead of argparse

Signed-off-by: Andrew Schoen <aschoen@redhat.com>
adding tests for teuthology.ls, coverage now at 88%

Signed-off-by: Andrew Schoen <aschoen@redhat.com>
Merge pull request #360 from andrewschoen/docopt-ls

port teuthology-ls to use docopt instead of argparse