Instead of lines between edges, use paths.

For each link/edge between nodes, calculate a linknum. This is used to
adjust the arc between nodes so that multiple edges between nodes don't
overlap.

in graphConf there's a use_curved_edges variable. Setting to true will
enable curved edges.

Tweaked the CSS so that paths display and aren't filled.

I also auto-linted graph_viz.js at some point which made a bunch of
spacing changes, didn't realize at the time that this might be an issue.

css/graphStyle.css

@@ -49,12 +49,18 @@
   fill: none;
   pointer-events: all;
 }
-/*
+
 .links line {
   stroke: #999;
   stroke-opacity: 0.6;
 }
 
+path {
+  fill: none;
+}
+
+/*
+
 .nodes circle {
   stroke: #fff;
   stroke-width: 1.5px;

scripts/graphConf.js

@@ -39,3 +39,4 @@ const node_position_y = 'graphexpy'
 const default_edge_stroke_width = 3;
 const default_edge_color = "#CCC";
 const edge_label_color = "#111";
+const use_curved_edges = true;

scripts/graphShapes.js

@@ -179,7 +179,7 @@ var graphShapes = (function(){
 
 	function decorate_link(edges,edgepaths,edgelabels){
 
-		var edges_deco = edges.append("line").attr("class", "edge").classed("active_edge",true)
+		var edges_deco = edges.append("path").attr("class", "edge").classed("active_edge",true)
 			.attr("source_ID",function(d) { return d.source;})
 			.attr("target_ID",function(d) { return d.target;})
 			.attr("ID",function(d) { return d.id;});