merge in new ads
fixes #10961: change variable names in grid docs
Merge branch 'master' of github.com:twbs/bootstrap
update gitignore to restore the ruby-version ignore and rename section to all docs stuff
Merge branch 'master' of github.com:twbs/bootstrap

Conflicts:
	css.html
run grunt
Fixes #10959: round the .lead values down to nearest pixel via floor()
Merge branch 'master' of github.com:twbs/bootstrap