v1.5.0

• Added Viewer.spin command to spin the camera around an axis
• Relax some limits on number of elements that could be rendered at full connectivity level. Now it would theoretically be possible to render 2^24 atoms, even though the amount of geometry is likely to take down the browser.
• Fix rendering for very long RNA molecules that broke some assumptions in the cartoon rendering code (1J5E, for example see issue #82).
• Improve heuristics to determine whether two residues belong to the same trace by not introducing trace breaks in case the residues are connected by a bond. This allows users to manually set bonds in case they have other means of knowing that two residues are to part of the same trace (#83).