Fix rendering of graphs on retina displays. Fixes #72.
Fix rendering of graphs on retina displays. Fixes #72.

Forces canvas element to scale up its height & width according to
window.devicePixelRatio (1 - normal, 2 - retina). In-line CSS forces
graph to stay the same on the page, while having twice the pixel
density.

multigraph/js-multigraph,henhouse/js-multigraph,henhouse/js-multigraph,henhouse/js-multigraph,multigraph/js-multigraph,multigraph/js-multigraph