upgrade to cytoscape.js 2.3.1

[Dan Bean]

doesn't correctly render saved networks - even if saved with this version. Probably something to do with model position vs rendered position in data that was handled differently in older versions.

[Dan Bean]

fix for node positions: instead of cy.load(), remove all elements then use cy.add(). Cy.load() could possibly be used if the init layout is set to "preset", not tested.

[Dan Bean]

fix for node label: use eles.flashClass() to temporarily add a node style class with css: content: " ", then go back to the old class with content: data(name). This forces the renderer to update the label content

[Dan Bean]

new cytoscape versions fix these bugs