New upstream release 1.4.0
    
    - https://github.com/cloudhead/less.js/blob/master/CHANGELOG.md
    - support for :extend() in selectors (e.g. input:extend(.button) {}) and &
      :extend(); in ruleset (e.g. input { &:extend(.button all); })
    - maths is now only done inside brackets. This means font: statements, media
      queries and the calc function can use a simpler format without being escaped.
      Disable this with --strict-maths-off in lessc and strictMaths:false in
      JavaScript.
    - units are calculated, e.g. 200cm+1m = 3m, 3px/1px = 3. If you use units
      inconsistently you will get an error. Suppress this error with
      --strict-units-off in lessc or strictUnits:false in JavaScript
    - (~"@var") selector interpolation is removed. Use @{var} in selectors to have
      variable selectors
    - default behaviour of import is to import each file once. @import-once has
      been removed.
    - You can specify options on imports to force it to behave as css or less
      @import (less) "file.css" will process the file as less
    - variables in mixins no longer 'leak' into their calling scope
    - added data-uri function which will inline an image into the output css. If
      ieCompat option is true and file is too large, it will fallback to a url()
    - significant bug fixes to our debug options
    - other parameters can be used as defaults in mixins e.g. .a(@a, @b:@a)
    - an error is shown if properties are used outside of a ruleset
    - added extract function which picks a value out of a list,
      e.g. extract(12 13 14, 3) => 3
    - added luma, hsvhue, hsvsaturation, hsvvalue functions
    - added pow, pi, mod, tan, sin, cos, atan, asin, acos and sqrt math functions
    - added convert function, e.g. convert(1rad, deg) => value in degrees
    - lessc makes output directories if they don't exist
    - lessc @import supports https and 301's
    - lessc "-depends" option for lessc writes out the list of import files used in
      makefile format
    - lessc "-lint" option just reports errors
    - support for namespaces in attributes and selector interpolation in attributes
    - other bug fixes
    - strictUnits now defaults to false and the true case now gives more useful but
      less correct results, e.g. 2px/1px = 2px
    - Process ./ when having relative paths
    - add isunit function for mixin guards and non basic units
    - extends recognise attributes
    - exception errors extend the JavaScript Error
    - remove es-5-shim as standard from the browser
    - Fix path issues with windows/linux local paths
    - change strictMaths to strictMath. Enable this with --strict-math=on in lessc
      and strictMath:true in JavaScript.
    - change lessc option for strict units to --strict-units=off
    - fix passing of strict maths option