<bugfix>Fix connection drawing issue on Mac</bugfix> <ticket>#538</ticket>
<bugfix>Fix connection drawing issue on Mac</bugfix>
<ticket>#538</ticket>

Perturb the second control point's y position slightly so that we don't run into the Mac OS? issue where the Bezier curve seems to cross over itself (looks like a twisted ribbon).

gui/pipeline_view.py:
  - QGraphicsConnectionItem.create_path: perturb the y coordinate
    slightly on the second control point

Nikea/VisTrails,VisTrails/VisTrails,Nikea/VisTrails,minesense/VisTrails,celiafish/VisTrails,hjanime/VisTrails,minesense/VisTrails,VisTrails/VisTrails,minesense/VisTrails,hjanime/VisTrails,celiafish/VisTrails,minesense/VisTrails,VisTrails/VisTrails,hjanime/VisTrails,Nikea/VisTrails,celiafish/VisTrails,Nikea/VisTrails,hjanime/VisTrails,celiafish/VisTrails,hjanime/VisTrails,minesense/VisTrails,VisTrails/VisTrails,VisTrails/VisTrails