fix main.html
Merge branch 'gacco2/master' of https://github.com/WatanabeYasumasa/edx-platform into gacco2/master
Merge branch 'gacco2/master' of https://github.com/WatanabeYasumasa/edx-platform into gacco2/master
Merge branch 'gacco2/master' of https://github.com/WatanabeYasumasa/edx-platform into gacco2/master
Merge branch 'gacco2/master' of https://github.com/WatanabeYasumasa/edx-platform into gacco2/master
Merge branch 'gacco2/master' of https://github.com/WatanabeYasumasa/edx-platform into gacco2/master
fix navigation.html