Use underscore-plus from browser process classes

src/browser/application-menu.coffee

@@ -1,7 +1,7 @@
 app = require 'app'
 ipc = require 'ipc'
 Menu = require 'menu'
-_ = require 'underscore'
+_ = require 'underscore-plus'
 
 # Private: Used to manage the global application menu.
 #

src/browser/atom-application.coffee

@@ -11,7 +11,7 @@ path = require 'path'
 net = require 'net'
 url = require 'url'
 {EventEmitter} = require 'events'
-_ = require 'underscore'
+_ = require 'underscore-plus'
 
 socketPath = '/tmp/atom.sock'
 

src/browser/atom-window.coffee

@@ -5,7 +5,7 @@ dialog = require 'dialog'
 ipc = require 'ipc'
 path = require 'path'
 fs = require 'fs'
-_ = require 'underscore'
+_ = require 'underscore-plus'
 
 # Private:
 module.exports =