Merge branch 'kalite' of https://github.com/fle-internal/fle-home into kalite
Merge branch 'kalite' of https://github.com/fle-internal/fle-home into kalite
Increase sub-nav bar menu size, take out underline decorations, remove white background and add a divider line stead
Tweak spacing and grids. Modify the exereicse pictures.
Replace offline learning picture.
Modify the customize text content.
Merge remote-tracking branch 'guan/kalite' into kalite

Conflicts:
	fle_site/apps/ka_lite/templates/ka_lite/sections/overview.html