initial grunts file to run regression tests

originally done in a shell script
discard stdout for pdfgen because it causes grunt to fall over
remove genhtml dependency
add option to generate CSS coverage info
add compile task that generates CSS for all books
simplify task names
addition of Appendix CSS for headers/subheaders and associated fixes
Tables now render numbering in the answer key
add error checking to make sure prereq files exist
better error handling when prereq file is missing
add color when skipping and add task descriptions
show the number of differences found for each book
update TODO and example config file
add prereq checking
make the prepare and diff tasks support a single book
add instructions for using grunt
fixes for learning objectives top/bottom margins/padding and fixes for padding inside table cells
Merge pull request #195 from Connexions/economics-bugfixes

Economics bugfixes
tidy up the glossary slots a bit
tidy up whitespace