use @screen-small var in grid.less

Per comment by @nextgenthemes on/in cd06c5baac64a366
Merge pull request #7782 from cvrebert/patch-1

use @screen-small var in grid.less
Fixes #7783: nuke bottom margin on fixed-bottom-navbar
Merge branch '3.0.0-wip' of github.com:twitter/bootstrap into 3.0.0-wip
correct right nav in navbar examples
fixed not working example code for modals
add offcanvas layout example based on bradfrost/this-is-responsive
Merge pull request #7798 from mediafreakch/3.0.0-wip

fixed not working example code for modals
Updated URL for jekyll installation
Merge pull request #7806 from koenpunt/patch-1

Updated URL for jekyll installation
Outdent nav links a bit more so they line up in navbar
Merge branch '3.0.0-wip' of github.com:twitter/bootstrap into 3.0.0-wip
Update config after updating to jekyll 1.0.1
Require .btn-default for regular buttons

* Instead of , use  for standard, gray button
* Improves ability to customize buttons by encouraging folks to not override .btn and thus overriding all button modifier classes
* Updates docs to reflect the change
* Reorganize buttons CSS
Fixes #7796: change @list-group-active-text to @list-group-active-color
nuke the unused navbar that was leftover
Update forms

* Overhaul the form control sizing section to only show sizing via grid columns as parents, not as classes on inputs
* Restore the inline-form option
* Restore the bottom margin on form controls and make them block level instead of inline-block
* More misc docs cleanup for forms
indentation fix
add offcanvas layout example based on bradfrost/this-is-responsive
Merge branch 'offcanvas-example' of github.com:trumbitta/bootstrap into offcanvas-example