Mention that Python needs to be in PATH for Pygments to work and thus jekyll not fail.

Update less.js to v1.5.1.

Build process: use module "load-grunt-tasks" to load grunt tasks

This fixes an error with `&:extend(.clearfix all)` when using the customizer.

enable strictMath in grunt-contrib-less config

more LESS strictMath fixes

<3 @seven-phases-max for helping to confirm & debug this
X-Ref: https://github.com/less/less.js/issues/1725

improve compliance with LESS's strictMath

Drop grunt-recess for grunt-contrib-less

Conflicts:
	Gruntfile.js
	package.json

more nesting in .list-group-item-variant mixin

Conflicts:
	Gruntfile.js
	dist/css/bootstrap-theme.min.css
	dist/css/bootstrap.min.css

Original discussion:
https://github.com/less/less.js/issues/1437#issuecomment-21383639.

Since we’re switching to `grunt-contrib-less`, we can take advantage of
newer LESS features than what RECESS supported. Included in that is the
ability to `:extend`, and not only that, but `:extend(.mixin-name
all)`. By doing so, we remove duplicate CSS for all our elements that
were being clearfix-ed.

Fixes #8947, #8968, #8991, #9257, #9268, #9291, #9430, #9604, #9686,
#9929, #10731, #10793, #11305, #11498, #11533, #11570, #11604, #11652.

(dem issues, tho)

Conflicts:
	dist/css/bootstrap.min.css