WIP : work on ControlContainer

 - can add nested containers
 - can add text and bare sliders
 - can retrieve both containers and widgets via qualified name

Still need to write code to create various control widgets.
ENH : added proto-type of enhanced slider class
ENH : added combo box widget

 - can add to ControlContainer
WIP : more prototyping work

 - proof-of-concept of class factory
 - proof-of-concept for building control boxs + plumbing
BLD : fixed up setup.py

 - patched up qt imports
ENH : fleshed out PairSpinner

 - pair of (double)spin boxes (value + step)
ENH : converted stack1D demo to use some new widgets

 - makes use of ControlContainer
 - uses PairSpinners
DOC : minor doc changes
Merge pull request #15 from tacaswell/control_widget

Control widgets