updated changelog to reflect changes since version 1.2
Improved code for manually specifying output file name.
added code to save nBackscatteredRays to output matfile

This is broken -it generates corrupted matfiles when running CTL
computations.
Will fix in (near!) future.
Minor changes.
moved caseTitle into options struct.
moved opening of output file up one level to cTraceo.c

The case title is now also written to the output file in cTraceo.c.
In fact a bug has now been solved: the user defined caseTitle was not
actually being written to the output file. The output type (RCO,ARI, etc)
was being written.