Update sigma.parsers.gexf.js

Need to do : 
obj.y = - obj.viz.position.y; 

Otherwise the graph is up side down compared to what you had in gephi. Can be annoying for map for example.
Add timeout for Firefox to dragNodes plugin.  Closes #278.
Fix for overlapping nodes not being draggable
Fix case where initial node isn't considered current when it hasn't been left after entering/exiting an overlapping node
Remove check for over/outNode occurring multiple times. Unnecessary.
Fix comments
Better variable name for array of hovered nodes
Rework of hover logic to allow a single label to be displayed
Add self referenced nodes edge rendering.
add right click events

Add rightClick, rightClickStage, rightClickNode, and rightClickNodes
events
Merge remote-tracking branch 'origin/master' into captors-mouse-right-click
Add captor data to events

Add ctrlKey, shiftKey, altKey, metaKey to captor data and add captor
data to dispatched events.
add 'renderers custom edge shapes' plugin
add tapered edges
update README
Add graph.attachBefore
add graph.adjecentNodes and adjacentEdges
add the filter plugin
add the example
add i/o and fix minor stuff