Release @google-cloud/asset v0.3.0 (#121)

* Release v0.3.0

* Update CHANGELOG.md

Author: jkwlui

asset/snippets/package.json

@@ -15,7 +15,7 @@
     "test": "mocha system-test --timeout 20000"
   },
   "dependencies": {
-    "@google-cloud/asset": "^0.2.1",
+    "@google-cloud/asset": "^0.3.0",
     "@google-cloud/storage": "^2.3.0",
     "uuid": "^3.3.2",
     "yargs": "^13.0.0"