Fixes #7943: typo in makefile
remove make gh-pages command
Bring the customizer up to speed

I reworked the customizer to match the new docs layout and include all
newly added variables, etc.
Would be glad to keep an eye on Customize and update it as v3 changes.
Help blocks in my new version need some more work, too, so this is just
a basis.
Merge branch '3.0.0-wip' of https://github.com/juthilo/bootstrap-wip into 3.0.0-wip
delete customize layout since it's no longer in use
Merge branch '3.0.0-wip' of github.com:twitter/bootstrap into 3.0.0-wip