Update image list to fetch images from GitHub

test/markdown_image_list.test.coffee

@@ -16,7 +16,7 @@ list = null
 describe 'markdown_image_list.coffee', ->
 
     beforeEach ->
-        list = new MarkdownImageList
+        list = new MarkdownImageList {}, client:{fetchFile:sinon.stub().returns(w.promise(->))}
 
     describe '_analyzeMarkdownText', ->
 

test/test_helper.coffee

@@ -16,6 +16,7 @@ global.Backbone = require 'backbone'
 global.assert   = chai.assert
 global.expect   = chai.expect
 global.should   = chai.should()
+global.sinon    = require 'sinon'
 global.util     = require 'util'
 global.w        = require 'when'