Preliminary bridge diagrams.
Increased left margin and slider size.
Disallow selection of text (especially on double-click)
Edit elements now look proper on firefox.

Using <img>s instead of <image> svg elements.
Using two img for add/remove instead of reusing one.
Merge branch 'master' into deploy_client
Updated d3.js to version 3.3.4
Merge branch 'master' into deploy_client