docs(readme): add Greenkeeper badge

README.md

@@ -1,6 +1,8 @@
 Piskel
 ======
 
+[![Greenkeeper badge](https://badges.greenkeeper.io/juliandescottes/piskel.svg)](https://greenkeeper.io/)
+
 [![Travis Status](https://api.travis-ci.org/juliandescottes/piskel.png?branch=master)](https://travis-ci.org/juliandescottes/piskel) [![Built with Grunt](https://cdn.gruntjs.com/builtwith.png)](http://gruntjs.com/)
 
 A simple web-based tool for Spriting and Pixel art.

package.json

@@ -28,30 +28,30 @@
   },
   "devDependencies": {
     "dateformat": "2.0.0",
-    "fs-extra": "1.0.0",
-    "grunt": "^0.4.5",
+    "fs-extra": "3.0.1",
+    "grunt": "^1.0.1",
     "grunt-casperjs": "^2.2.1",
-    "grunt-contrib-clean": "1.0.0",
+    "grunt-contrib-clean": "1.1.0",
     "grunt-contrib-concat": "1.0.1",
     "grunt-contrib-connect": "1.0.2",
     "grunt-contrib-copy": "1.0.0",
     "grunt-contrib-jshint": "1.1.0",
-    "grunt-contrib-uglify": "1.0.1",
+    "grunt-contrib-uglify": "2.3.0",
     "grunt-contrib-watch": "1.0.0",
-    "grunt-include-replace": "4.0.1",
-    "grunt-jscs": "2.8.0",
-    "grunt-karma": "1.0.0",
+    "grunt-include-replace": "5.0.0",
+    "grunt-jscs": "3.0.1",
+    "grunt-karma": "2.0.0",
     "grunt-leading-indent": "0.2.0",
     "grunt-nw-builder": "3.1.0",
     "grunt-open": "0.2.3",
     "grunt-replace": "1.0.1",
-    "grunt-spritesmith": "6.3.0",
-    "jasmine-core": "2.1.0",
-    "karma": "1.3.0",
-    "karma-chrome-launcher": "1.0.1",
-    "karma-jasmine": "1.0.2",
-    "karma-phantomjs-launcher": "0.2.3",
-    "load-grunt-tasks": "3.5.0",
+    "grunt-spritesmith": "6.4.0",
+    "jasmine-core": "2.6.1",
+    "karma": "1.7.0",
+    "karma-chrome-launcher": "2.1.1",
+    "karma-jasmine": "1.1.0",
+    "karma-phantomjs-launcher": "1.0.4",
+    "load-grunt-tasks": "3.5.2",
     "phantomjs": "2.1.7",
     "phantomjs-polyfill-object-assign": "0.0.2",
     "promise-polyfill": "6.0.2",