fix bug in chunk options for statistics.lyx
work around knitr bug exposed by neurons vignette

* hook_rgl does not create figure/ subdirectory
(I hadn't noticed this because it existed in my project)
Fix README coin link, add links to cached copies of vignette
ignore vignette intermediates

* including all latex outputs
fix cross-reference to gphys package

* I think the explicit \link[gphys]{} is required
  because gphys is not loaded by default. It is only
  a suggested package loaded when building vignette.
News and description for v0.2.1