updates to the Jenkins WAR file need to restart the runit service
jenkins_node: ensure default exists for url attribute

We need to ensure a sane default is set even if 
the server url attribute is not set on the node 
object.
refactor jenkins_job provider

* make helper methods private
* do some basic validation on the user provided config file before 
attempting to IO.read it.
* simplify :create, :update actions
update WIP README with TODO and Proposed Test Scenarios