Fix CLI exit code

The 'lettuce' CLI, after a successful test run, was always exiting with
an exit status of 1 indicating an error. The main() function was
erroneously considering the test run a failure if the TotalResult
instance returned by runner.run() evaluated to True (which is always
does).

This issue was reported on the mailing list [1] by Dave Sykes. I ran
in to the same problem while running lettuce from tox which reports the
success/failure of a test run based on the exit status of the test
command (lettuce).

[1] https://groups.google.com/d/topic/lettuce-users/6Nu2QXE1MBc/discussion

Add tox.ini for tox (http://tox.testrun.org/)

Fix for situation where 'localhost' is not resolvable

 * Scenario instances now have a `self.previous_scenario` attribute pointing to the last full-featured scenario (if any)
 * the runner now takes tag names
 * Scenario have now a method that matches strings

removing public content that can possibly offend people. I am fully regretful of have written something that could offend someone. Sorry :(