Fixes #33: Multiple refreshes on job creation
Fixes #33: Multiple refreshes on job creation

I made the Queue class not update on method access as before, which
means the user now has to run Queue.update() to get the latest
information, not just Queue as before. This provides a dramatic speedup
as queue parsing is costly.

MikeDacre/python-cluster,MikeDacre/fyrd,MikeDacre/fyrd,MikeDacre/slurmy