fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-ASYNC-2441827
- https://snyk.io/vuln/SNYK-JS-LODASH-1018905
- https://snyk.io/vuln/SNYK-JS-LODASH-1040724
- https://snyk.io/vuln/SNYK-JS-LODASH-450202
- https://snyk.io/vuln/SNYK-JS-LODASH-567746
- https://snyk.io/vuln/SNYK-JS-LODASH-608086
- https://snyk.io/vuln/SNYK-JS-MINIMIST-2429795
- https://snyk.io/vuln/SNYK-JS-MINIMIST-559764

Author: snyk-bot

package.json

@@ -7,12 +7,12 @@
     "contentstack": "./bin/index.js"
   },
   "dependencies": {
-    "async": "2.6.1",
+    "async": "2.6.4",
     "chalk": "2.4.1",
     "commander": "2.9.0",
     "debug": "4.1.0",
-    "lodash": "4.17.11",
-    "mkdirp": "0.5.1",
+    "lodash": "4.17.21",
+    "mkdirp": "0.5.2",
     "ncp": "2.0.0",
     "prompt": "1.0.0",
     "request": "2.88.0",