Import all of the bootstrap framework with custom variables file.

bootstrap.less

/*!
 * Bootstrap (http://getbootstrap.com)
 * Copyright 2011-2016 Twitter, Inc.
 * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
 */
@version: 3.3.6;
@tag: v3.3.6;
@url:"https://raw.githubusercontent.com/twbs/bootstrap/@{tag}/less";

// Put a custom variable path
@custom-variables: "";

// Core variables and mixins
@import "@{url}/variables.less";
@import (optional) "@{custom-variables}";
@import "@{url}/mixins.less";

// Reset and dependencies
@import "@{url}/normalize.less";
@import "@{url}/print.less";
@import "@{url}/glyphicons.less";

// Core CSS
@import "@{url}/scaffolding.less";
@import "@{url}/type.less";
@import "@{url}/code.less";
@import "@{url}/grid.less";
@import "@{url}/tables.less";
@import "@{url}/forms.less";
@import "@{url}/buttons.less";

// Components
@import "@{url}/component-animations.less";
@import "@{url}/dropdowns.less";
@import "@{url}/button-groups.less";
@import "@{url}/input-groups.less";
@import "@{url}/navs.less";
@import "@{url}/navbar.less";
@import "@{url}/breadcrumbs.less";
@import "@{url}/pagination.less";
@import "@{url}/pager.less";
@import "@{url}/labels.less";
@import "@{url}/badges.less";
@import "@{url}/jumbotron.less";
@import "@{url}/thumbnails.less";
@import "@{url}/alerts.less";
@import "@{url}/progress-bars.less";
@import "@{url}/media.less";
@import "@{url}/list-group.less";
@import "@{url}/panels.less";
@import "@{url}/responsive-embed.less";
@import "@{url}/wells.less";
@import "@{url}/close.less";

// Components w/ JavaScript
@import "@{url}/modals.less";
@import "@{url}/tooltip.less";
@import "@{url}/popovers.less";
@import "@{url}/carousel.less";

// Utility classes
@import "@{url}/utilities.less";
@import "@{url}/responsive-utilities.less";