removed outline from modal
Customizable backdrop opacity
Added opacity to customizer and rebuilt customizer
Options of sizes added in modal
Adjust in modal size rules
Add well-border variable

Add a variable to allow the well border color to be specified.

The reason I'd like to see this included is that my companies styleguide
requires an explicit border color on well-like constructs. This variable
allows me to easily override the default to use that color.
Fix #11400 and #11431
Fixed single btn in btn-group-veritcal not being rounded
Reduce size of the visibility styles
Fixes #11669 - Adds smooth modal scrolling on iOS by default
Don't exclude fonts from bower installs

Excluding fonts/ from bower installs causes glyphicons to be
unavailable to projects using development Bootstrap LESS files.
Drop redundant module import
Add `.animation-*()` mixins
Remove unused variables.
hide space characters in input-group-btn to fix segmented buttons double border
Improve pager customization
Add new template, Cover
Issue #11852 : create a new variable for the list group active item link text.
use @zindex-modal for .modal and @zindex-modal-background for .modal-backdrop.
removed z-index for .modal-dialog, it was not necessary because the parent element (.modal) already has a z-index.
add dist files.