Fix adding of edges to graph in pushGraph (should be addEdge instead of addNode)
Use required ID attribute when parsing GEXF
Merge remote-tracking branch 'origin/pr/85'

* origin/pr/85:
  Use required ID attribute when parsing GEXF
Merge branch 'pr/73'

* pr/73:
  drop id, label from edges; check for edge attributes not in dict; store weight to size parameter
  add interpreter command make sure attr is in nodesAttributesDict edge ids can be duplicate in gexf exports of directed graphs, thus do not use the gexf edge id but increment a counter same as in parseGexf plugin
  add parseJSON plugin
  if edge weight is set, set size attribute to this value to make setting minEdgeSize and maxEdgeSize effective
  Fixing GEXF parsing in IE.
IE doesn't support overrideMimeType
IE doesn't support namespaces and getElementsByTagNameNS for XML, but it is still possible to retrieve namespaced nodes using getElementsByTagName with a 'theNamespace:theNodeName' argument.
FireFox needs a URI, but all browsers support the viz:* syntax as it turns out, so use that
Merge branch 'pr/89'

* pr/89:
  IE doesn't support overrideMimeType
minor change
Merge remote-tracking branch 'jacomyal/master'