Use less NPM module instead of vendored less

We're currently using nathansobo's fork, which doesn't depend on
`window` being undefined to operate in Node mode.

package.json

@@ -17,7 +17,8 @@
     "spellchecker": "0.3.0",
     "pathwatcher": "0.3.0",
     "plist": "git://github.com/nathansobo/node-plist.git",
-    "space-pen": "git://github.com/nathansobo/space-pen.git"
+    "space-pen": "git://github.com/nathansobo/space-pen.git",
+    "less": "git://github.com/nathansobo/less.js.git"
   },
 
   "private": true,

src/app/window.coffee

@@ -2,7 +2,7 @@ fs = require 'fs'
 fsUtils = require 'fs-utils'
 $ = require 'jquery'
 _ = require 'underscore'
-{less} = require 'less'
+less = require 'less'
 require 'jquery-extensions'
 require 'underscore-extensions'
 require 'space-pen-extensions'
@@ -142,7 +142,7 @@ window.requireStylesheet = (path) ->
 window.loadStylesheet = (path) ->
   content = fsUtils.read(path)
   if fsUtils.extension(path) == '.less'
-    (new less.Parser).parse content, (e, tree) ->
+    (new less.Parser({})).parse content, (e, tree) ->
       throw new Error(e.message, path, e.line) if e
       content = tree.toCSS()