Upgrade django-haystack to 2.7.0
Upgrade django-haystack to 2.7.0

2.4.0 did not have official django 1.10 support, and the full text
search currently crashes, and that no longer happens with this version.

2.7.0 is also the last release to support django 1.10

stianjensen/wikipendium.no,stianjensen/wikipendium.no,stianjensen/wikipendium.no