Feature/31 replace d3 first part

Initial pass at replacing D3 rendering with custom SVG via Aurelia custom elements.

New graph component now uses d3 to compute a static layout
Node and Edge deltas are data bound to new Node and Edge custom elements respectively
Display, Animation, Interaction behaviour are now provided by the Node and Edge custom elements
GSAP TweenMax and Attribute plugin is used for animation
Upgraded to latest Aurelia beta

Remaining TODO items in this issue will be tackled one at a time as separate items, as per priority.

Fixes #31

CANVE / canve-viz