fix transparency after drawing a picking scene
add code to show bounding spheres

This code is meant for debugging of the auto-slabbing code.
pull auto-slabbing code out of viewer
fix auto-slabbing when molecules are off-center

Closes issue #45.
a little more reasonable defaults for fog
another stab at strand smoothing
implement arrow heads for strands
update README
fix hex colour parser
mainAxes exists on the cam object, not the PV object.
fix a few typos
add method to get current atom color

It uses the trace/atom assoc to figure out what the color of an atom
currently is. It will have to run through the whole assoc, because
we don't maintain a map from atom to vertex assoc entry. This can
potentially get slow when requesting the color of many atoms. If
that use-case every comes up, we might add a specialized method to
do that which runs over the vert assoc once and builds a map.
add new feature to README.md
start outlining multi-resolution model support
add low-resolution model format
first version of low-resolution display

The complete HIV capsid can be displayed in the browser. It's
rather ugly and many things are not correctly displayed
(transition from secondary structure element to coil, and
connectivity betweeen chains).. But it's a good start. Next:
laying out a proper data structure for storing the multi-
resolution model.
add proper data structure for low-resolution model

now the before-mentioned artifacts are gone and the HIV
capsid is shown in it's full glory.
update mrm file format to contain chain names
rename traces to backboneTraces to match mol.MolBase
low res model can be passed to trace/lineTrace as well