Update travis to use Node 0.10.x vs 0.8.x

This fixes failures related to failed npm installations when trying to run
a travisci build against new branches.
Add xmlns attributes to svg and defs elements

I want to export glimpse.js svg graphs to images but to do this the
xml must be valid. To make valid xml it requries specifying the xmlns attributes.

Look here for more info: https://github.com/mbostock/d3/issues/1935

JSHint