Reorganized setup.py code
Added "deb" setup command
more reorganization to make setup-helpers code more generic
Updated build system to use pybuild
- now generates python-pyqtgraph, python3-pyqtgraph, and python-pyqtgraph-doc packages
- `python setup.py sdist deb` works
remove tools/debian; will add a new branch with debian/ at the root.
copy setHelpers.py changes from debian/ branch
Merge branch 'deb_build' into develop

- removes the tools/debian directory (re-added in debian branch)
- updates to setup scripts
- Fixed FillBetweenItem to force PlotCurveItem to generate path
- Added FillBetweenItem.setCurves()
- Added FillBetweenItem example
py2.6 fix in setupHelpers
quiet setup.py warning about install_requires
remove print
Merge branch 'deb_build' into develop
Minor setup corrections
Fix imports in MultiPlotWidget and its example.
Merge remote-tracking branch 'termim/develop' into multiplotwidget-fix
Fix MultiPlotWidget wrapping methods incorrectly.
MultiPlotWidget now uses scroll bar when plots do not fit in widget area.
Added setMinimumPlotHeight method, set default min height to 50px.
Merge branch 'multiplotwidget-fix' into develop
Import and py3 bugfixes for MultiPlotWidget
Add setMinimumPlotHeight method.
Implementing user-defined limits for ViewBox
Basic view limits appear to be working.
Removed duplicate limit-setting arguments
Renamed args for clarity, improved documentation
Fixed interaction bugs
 - zooming works correctly when view is against limit
 - no more phantom target range; target is reset during mouse interaction.
Typo