Add yarn & node to engines (#135)

* Add yarn & node to engines

* Bump node version in travis.yml

* yarn ^1.3.2

* Update dependencies

.travis.yml

@@ -1,6 +1,6 @@
 language: node_js
 node_js:
-  - "9"
+  - "10"
 cache:
   yarn: true
   directories:

package.json

@@ -1,6 +1,10 @@
 {
   "version": "0.22.7",
   "private": true,
+  "engines": {
+    "node": "^10.1.0",
+    "yarn": "^1.3.2"
+  },
   "workspaces": [
     "packages/*"
   ],
@@ -11,6 +15,6 @@
     "test": "jest --coverage"
   },
   "devDependencies": {
-    "@polkadot/dev": "^0.19.18"
+    "@polkadot/dev": "^0.19.24"
   }
 }

yarn.lock

@@ -664,9 +664,9 @@
     lodash "^4.17.5"
     to-fast-properties "^2.0.0"
 
-"@polkadot/dev@^0.19.18":
-  version "0.19.18"
-  resolved "https://registry.yarnpkg.com/@polkadot/dev/-/dev-0.19.18.tgz#f03861c66ce246851b1f96a6b5f0167747b6d3f4"
+"@polkadot/dev@^0.19.24":
+  version "0.19.24"
+  resolved "https://registry.yarnpkg.com/@polkadot/dev/-/dev-0.19.24.tgz#c9e97a3d9c019c1978d1db4ce0ec9c936ca36998"
   dependencies:
     "@babel/cli" "^7.0.0-beta.47"
     "@babel/core" "^7.0.0-beta.47"