fontdiff should highlight all changes inside a line

[brawer]

With the attached fonts and specimen, fontdiff correctly detects all lines that have changed, but then it only highlights some parts of the change. @iverg, since you’ve written the code that colorizes chunks of text inside a single line, can you have a look?

fontdiff --before A.ttf --after B.ttf --specimen specimen.html --out out.pdf

The files for reproducing this bug are here.

[xiangyexiao]

Is https://github.com/googlei18n/fontdiff/issues/14 related to this bug?

[xiangyexiao]

@marekjez86