Fix Yeoman-environment and refactor some code (#20)

* Refactor .ts code

* Change yeoman-environment to 2.10.3

package.json

@@ -134,9 +134,9 @@
         "@types/node": "^7.0.43",
         "chai": "^4.1.2",
         "lodash": "^4.17.11",
-        "mocha": "^3.5.3",
+        "mocha": "^9.1.3",
         "ts-node": "^6.0.3",
-        "typescript": "~2.8.4",
+        "typescript": "^3.5.1",
         "vscode": "^1.1.30",
         "xml2js": "^0.4.19"
     },
@@ -154,6 +154,6 @@
         "run-async": "^2.0.0",
         "semver": "^5.0.3",
         "strip-ansi": "^3.0.0",
-        "yeoman-environment": "^1.5.2"
+        "yeoman-environment": "2.10.3"
     }
 }

src/yo/yo/yo.ts

@@ -92,7 +92,7 @@ export default class Yeoman {
 			generator = generator.slice(prefix.length);
 		}
 
-		return new Promise((resolve, reject) => {
+		return new Promise<void>((resolve, reject) => {
 			Promise.resolve(window.showQuickPick(new Promise((res, rej) => {
 				setImmediate(() => {
 					try {