Follow up to reverted commits

Revert commits

Bootstrap is being relicensed from Apache 2.0 to MIT so that more of our community can use the free and open source software we lovely create together. As commits are copyright their original authors, the commits of any individual not agreeing to relicense their contributions are being removed to be later rewritten by the @twbs/team.

This undoes the changes introduced by the following commits:
https://github.com/twbs/bootstrap/commit/7ea34ae0ef79c793e9a9d393b4eef825b71e84b5 , https://github.com/twbs/bootstrap/commit/7376eef378fe7d5e69b8b8cce93c7c64b751d55a , https://github.com/twbs/bootstrap/commit/303ba1326bbe367598ab4cc063b4607507208e56 , https://github.com/twbs/bootstrap/commit/7d1c8c2a0ce16331583a965821690f7715e62908 , https://github.com/twbs/bootstrap/commit/11319f6da9f9a19ec40743cdfe868ac732698149 , https://github.com/twbs/bootstrap/commit/110fc8860117d8675345806219ba313b18086db2 , https://github.com/twbs/bootstrap/commit/ced08f69359f3a70771804a98fa3c499f388cc74

Require comma on left side

enable CSS source maps in grunt-contrib-less

Conflicts:
	Gruntfile.js

fix href of "Browser and device support"

Fix handling of .btn-group placed inside .input-group-btn

Downgrade Safari and OS X

Fix handling of btn-group placed inside input-group-btn (used for mixing dropdowns with normal buttons)

move Sauce test browsers list out of Gruntfile into separate file

use S3-cached Jekyll install to further speed up the Travis build

minor refactoring of 4ee93c9f

make S3 caching significantly more generic