* Enabled acid2 on mac + linux. Updated the reference image. The only difference from the
real acid2 now is the paint order and a 1 pixel horizontal offset on the nose.
* Change line-height to be calculated correctly.
* Apply enclosing element style to text fragments.
This still needs a lot of work, but it covers the basic
cases and improves wikipedia while passing all existing tests.
Tweak reftest to deal with linux/travis black background.