fix(package): update yeoman-generator to version 3.1.0

Closes #64

Author: greenkeeper[bot]

package.json

@@ -31,7 +31,7 @@
     "generator-pattern-lab-starter": "git+https://[email protected]/phase2/generator-pattern-lab-starter.git#a626d763d9619228de3ea56c1ee9b804ff7ef131",
     "lodash": "^4.17.4",
     "semver": "^5.3.0",
-    "yeoman-generator": "^1.1.0",
+    "yeoman-generator": "^3.1.0",
     "yosay": "^2.0.0"
   },
   "devDependencies": {