Visual regression after gh-50 enabled permalinks for all headers

[erlend-aasland]

#50 introduced a visual regression.

After #50:

Before #50:

See also:

• add missing search page, properly link it #50 (comment)

[erlend-aasland]

@hodgestar #50 (comment):

Perhaps we can just style them better? Being able to link to subheadings on pages is nice.

[mattip]

Thanks for pointing it out. I only did half the sync with the pypy/pypy.org site styling, #52 should make it look better.