package: update dev dependencies to latest

package.json

@@ -3,8 +3,8 @@
   "version": "2.3.0",
   "description": "Client-side Bitcoin JavaScript library",
   "main": "./src/index.js",
-  "engines" : {
+  "engines": {
-    "node" : ">=0.12"
+    "node": ">=0.12"
   },
   "keywords": [
     "bitcoin",
@@ -64,12 +64,12 @@
     "wif": "^2.0.1"
   },
   "devDependencies": {
-    "async": "^1.5.0",
+    "async": "^2.0.1",
-    "bs58": "^2.0.1",
+    "bs58": "^3.0.0",
     "cb-http-client": "^0.2.0",
-    "httpify": "^1.0.0",
+    "httpify": "^3.0.0",
     "minimaldata": "^1.0.0",
-    "mocha": "^2.2.0",
+    "mocha": "^3.1.0",
     "nyc": "^8.1.0",
     "proxyquire": "^1.4.0",
     "sinon": "^1.12.2",