Update: maintain dependencies via Greenkeeper

* chore(package): update dependencies

https://greenkeeper.io/

* docs(readme): add Greenkeeper badge 

https://greenkeeper.io/

* chore: end testing node < 4

.travis.yml

@@ -6,9 +6,6 @@ addons:
     packages:
     - g++-4.8
 node_js:
-- '0.10'
-- '0.12'
-- iojs
 - '4'
 - '5'
 - '6'

README.md

@@ -1,5 +1,7 @@
 # node-jose #
 
+[![Greenkeeper badge](https://badges.greenkeeper.io/cisco/node-jose.svg)](https://greenkeeper.io/)
+
 A JavaScript implementation of the JSON Object Signing and Encryption (JOSE) for current web browsers and node.js-based servers.  This library implements (wherever possible) all algorithms, formats, and options in [JWS](https://tools.ietf.org/html/rfc7515 "Jones, M., J. Bradley and N. Sakimura, 'JSON Web Signature (JWS)' RFC 7515, May 2015"), [JWE](https://tools.ietf.org/html/rfc7516 "Jones, M. and J. Hildebrand 'JSON Web Encryption (JWE)', RFC 7516, May 2015"), [JWK](https://tools.ietf/html/rfc7517 "Jones, M., 'JSON Web Key (JWK)', RFC 7517, May 2015"), and [JWA](https://tools.ietf/html/rfc7518 "Jones, M., 'JSON Web Algorithms (JWA)', RFC 7518, May 2015") and uses native cryptographic support ([WebCrypto API](http://www.w3.org/TR/WebCryptoAPI/) or node.js' "[crypto](https://nodejs.org/api/crypto.html)" module) where feasible.
 
 <!-- START doctoc generated TOC please keep comment here to allow auto update -->

package.json

@@ -26,7 +26,7 @@
   ],
   "license": "Apache-2.0",
   "dependencies": {
-    "es6-promise": "^3.1.2",
+    "es6-promise": "^4.0.5",
     "jsbn": "^0.1.0",
     "lodash.assign": "^4.0.8",
     "lodash.clone": "^4.3.2",
@@ -41,42 +41,42 @@
     "long": "^3.1.0",
     "node-forge": "https://github.com/linuxwolf/forge/archive/browserify.tar.gz",
     "urlsafe-base64": "https://github.com/linuxwolf/urlsafe-base64/archive/encoding.tar.gz",
-    "uuid": "^2.0.1"
+    "uuid": "^3.0.1"
   },
   "devDependencies": {
     "browserify-istanbul": "^2.0.0",
     "chai": "^3.5.0",
     "conventional-changelog": "^1.1.0",
     "del": "^2.2.0",
     "gulp": "^3.8.10",
-    "gulp-eslint": "^2.0.0",
-    "gulp-istanbul": "^0.10.4",
-    "gulp-mocha": "^2.0.0",
+    "gulp-eslint": "^3.0.1",
+    "gulp-istanbul": "^1.1.1",
+    "gulp-mocha": "^3.0.1",
     "gulp-rename": "^1.2.0",
-    "gulp-uglify": "^1.1.0",
+    "gulp-uglify": "^2.0.1",
     "gulp-util": "^3.0.7",
     "istanbul": "^0.4.0",
     "jose-cookbook": "git+https://github.com/ietf-jose/cookbook.git",
     "json-loader": "^0.5.4",
     "karma": "^1.2.0",
-    "karma-chrome-launcher": "^0.2.3",
-    "karma-coverage": "^0.5.3",
-    "karma-firefox-launcher": "^0.1.4",
-    "karma-ie-launcher": "^0.2.0",
-    "karma-mocha": "^0.2.2",
+    "karma-chrome-launcher": "^2.0.0",
+    "karma-coverage": "^1.1.1",
+    "karma-firefox-launcher": "^1.0.0",
+    "karma-ie-launcher": "^1.0.0",
+    "karma-mocha": "^1.3.0",
     "karma-mocha-reporter": "^2.0.0",
-    "karma-safari-launcher": "^0.1.1",
-    "karma-sauce-launcher": "^0.3.1",
-    "karma-webpack": "^1.8.0",
+    "karma-safari-launcher": "^1.0.0",
+    "karma-sauce-launcher": "^1.1.0",
+    "karma-webpack": "^2.0.2",
     "lodash.bind": "^4.1.3",
     "lodash.clonedeep": "^4.3.2",
     "lodash.foreach": "^4.2.0",
-    "mocha": "^2.1.0",
+    "mocha": "^3.2.0",
     "run-sequence": "^1.0.2",
     "watchify": "^3.7.0",
     "webpack": "^1.13.2",
     "webpack-stream": "^3.2.0",
-    "yargs": "^4.6.0"
+    "yargs": "^6.6.0"
   },
   "browser": {
     "crypto": false