[BUGFIX] UI is eagerly consumed, but prompt (which costs a 100ms or s…

…o) is in-frequently used and so it should be required was late as possible

lib/ui/index.js

@@ -14,7 +14,6 @@ function UI(options) { // options === { inputStream, outputStream }
   var pleasantProgress = this.pleasantProgress = new PleasantProgress();
 
   this.through  = require('through');
-  this.Prompt   = require('inquirer').ui.Prompt;
   this.readline = require('readline2');
 
   // Output stream
@@ -38,7 +37,7 @@ UI.prototype.prompt = function(questions, callback) {
   var promtOutputStream = this.through(null, function() {});
   promtOutputStream.pipe(this.outputStream);
 
-  var Prompt = this.Prompt;
+  var Prompt = require('inquirer').ui.Prompt;
   // Note: Cannot move this outside
   //       Need a new readline interface each time, 'cause it gets torn down
   function PromptExt() {