New dim.im3d method - base::dim primitive handles dispatch
Additional test for reading/dimensions when read.im3d(,ReadData=FALSE)
Can now rely on dim(x) to do the right thing when x is an im3d
Change test setup so that tests involving remote download do not run on CRAN
Merge pull request #22 from ajdm/crantests

Change test setup so that tests involving remote download do not run on CRAN
Always add a bounding box and add non-null origin

* we often need to know at the other end whether an explicit origin was 
  specified
* this will now be tagged by the presence of an origin field
* bounding box will always be present
make sure that BoundingBox is always zapsmall()ed in im3d() constructor

* by putting it through boundingbox function
store explicit space origin when reading nrrd
Ensure amiramesh returns a 0 length integer/numeric vector when ReadData=FALSE

* use the first data block to determine type
don't try and simplify when we did not actually read any data
record the origin when reading amiramesh files
write out origin to nrrd when im3d has one
New SimplifyAttributes argument for read.im3d

* just return core attributes only
make sure that voxel dimensions/bounding box match Amira when any dim==1
Always store inferred origin when reading amiramesh files

* Amira does not store the "space origin" separately as is the case for nrrds
* Have decided that we should always store the origin inferred from the
  BoundingBox
Teach read.nrrd to accept logical values for ReadByteAsRaw argument
Give read.im3d a ReadByteAsRaw argument
Add test for complete equivalence of amiramesh and nrrd versions of data

* NB this data block was saved in Amira to both amiramesh and nrrd formats
change baseline to expect integer nrrds to be read in as R integers by default
Give read.amiramesh a ReadByteAsRaw argument