Increase size of circle

This increases the size of the circle so that it takes up most of the drawing
region, but still leaves room for the on hover numbers to appear. This makes it
more readable and easier to interact with. I may want to increase the size of
the backbone later.
Make plotting div not empty

This means that when the page loads we do not have the jmol window on the left
side until the diagram is loaded. This is a hack and should be replaced later
by having an animation while drawing which is removed when drawing completes.
Update rna2d.js lib
Remove mode toggle

Mode toggle is not needed with the new library. Thus we remove it from view.
Update code for new rna2d.js lib

The new lib takes a different data format to support having chains. This
requires changes in get_ordered_nts. In addition, the javascript interface is a
little different which is also updated here.