Create a docx target in the Makefile, so it can produce Word files too.

Hi Andrew, 

These changes to the Makefile should allow you to do `make` or `make docx` from the command line and automatically create a Word file as well as the other outputs. Test it in a non-critical directory :) You can do `make -n` or `make -n docx` to see the commands as they will be run, without actually executing any of them. 

Kieran