Update geocoder tests to match changing Google geocoder results.
Add test case which currently shows duplicates being returned.
Dedupe identical results
Add 'About' link to South Africa's 'Extras' menu

As requested in #985
Add 'Constituency Offices' link to 'Democracy Resources' nav
Merge branch 'issues/908-place-search-duplicates'
Merge branch 'extra-navbar-links'
reduced vertical height of carousel on homepage, #1004
Merge branch 'master' of git://git.mysociety.org/pombola into final-polish