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
improve compliance with LESS's strictMath
Merge pull request #11807 from twbs/stricter-math

improve compliance with LESS's strictMath
add parens around arithmetic in recursive mixin calls to comply with LESS strictMath

<3 @seven-phases-max for helping to confirm & debug this
X-Ref: https://github.com/less/less.js/issues/1725
misc strictMath compliance fixes
Merge pull request #11808 from twbs/strict-math-fixes

more LESS strictMath fixes
enable strictMath in grunt-contrib-less config
Merge pull request #11809 from twbs/enable-LESS-strictMath

enable strictMath in grunt-contrib-less config