Credentials optional, redirect support.

Made credentials optional - 'password' now only required if 'username' specified.  Some Jenkins instances configured without auth.
Added ability to follow redirects.  Jenkins can return a redirect when it receives a POST (i.e. to kick off a build).  This allows redirect to be followed so that 200 can be received
Update unit tests to handle optional creds
Ability to retrieve more job info.

Added ability to retrieve test results of a build job.  Since test results may or may not be available handling of the 404 result is handled inline and a nil is returned if there are no results.
Added ability to get detailed build info for a job
Maestro-ify the gem until pulled