use internal procedures for common tasks
added graphically diff which shows percentage.

Warning: It seems this approach is very slow.
Diffing a whole book takes too long with this approach.
add PIL(low) for image percentage diffing
fixing display and diff bugs for dirs. Add percentage diffing
Merge pull request #134 from Connexions/diff-pdf-image-percentage

Show diff pdf textual and graphical percentage
added svg feature assets for upcoming precalculus text
Merge pull request #135 from Connexions/precalculus-assets

Adding svg feature assets for upcoming precalculus text
Merge branch 'master' into production
added additional numbering file for sociology to reset numbering on short answer eoc section
added additional numbering file for sociology to reset numbering on short answer eoc section
removed unnecessary less/debugging variables from file
Merge pull request #136 from Connexions/sociology-numbering-fix

Reset of section numbering for Sociology Short Answer EOC questions
Merge branch 'master' into production