fix (and test) for read.neuron's failure to set InputFileName properly

* have fixed this both at source in read.neurons and at the final common path
  which was a do.call expression in as.neuron.ngraph
* includes a test
* fixes #62
read.neurons signals problem file and warns immediately

* fixes #61
* includes test for signalling the problem file
fix bug in reading amiramesh binary files with empty sections

* warning because there was no linefeed but rather an immediate null from next
  block of data
* so far this never resulted in any errors, but looks like it could have done
  in situations where next byte was not 0
* fixes #63
Test identity of neurons read in by read.neuron and read.neurons

* ensure that they are really identical by looking at everything except
  the CreatedAt field
test that we get a warning for neurons without width data

* only source of these at the moment is flycircuit
Divide up lengthy neuron i/o tests into 3 separate contexts
expect a warning when we can't overwrite
suppress warning that immediately precedes a test error

* trying to clean up warnings and this one is superfluous
remove a few more warnings in tests
Fix left over temporary file in xformpoints.cmtkreg

* this had been there for a while and was a classic case of on.exit not having
  the add=TRUE argument
* closes #65
Ensure tests do not leave temp files behind

* in combination with 5d550082d4e21630a127cfd39ad1709a1f376e12 fixes #64
Bump version 1.4.5
Ensure that urls in README.md are linked on CRAN

* github automatically makes links for any urls
Fix test that included a check for atime of a file read twice in succession

* noticed by Brian Ripley on Solaris
* MacOSX does not update the atime for this access
* other OSes may do the same or round time to nearest second
  (which would only result in rare failures)
Remove warnings by supplying vertex data for as.neuron.ngraph tests

* real neurons always have vertex data, but for convenience tests omitted this
* reveals a bug in as.neuron.ngraph
Fix handling of as.neuron.ngraph when vertexData does not have PointNo field

* test in previous commit checks for this behaviour
* add additional test for behaviour when vertexData has too many rows
  (and no PointNo field)
Bump version to 1.4.6