Add function to plot bounding box in 3D
Merge pull request #136 from ajdm/feature/plotboundingbox

Add function to plot bounding box in 3D
sty: tidying neuron-io test file
Check for file existence in read.im3d before reading

* throwing an error on failure
* this has the side-benefit of suppressing a warning in test for reading 
  non-existent file
Don't write invalid radius information

* warns when there are NAs in radius
* Amira fails to read files with NAs/NaNs
* +test
Merge branch 'master' of github.com:jefferis/nat

* 'master' of github.com:jefferis/nat:
  Add function to plot bounding box in 3D
roxygenise change 3e1dc5ed to export plot3d.boundingbox
Fix xformpoints.cmtkreg when input contains NAs

* fixes #132
* includes test
Install R, X11
Remove recommendation to use lab R repository

* master is pretty stable so just having CRAN and github should be fine
* also suggest using the github release branch