fix: package.json, package-lock.json & .snyk to reduce vulnerabilities

The following vulnerabilities are fixed with a Snyk patch:
- https://snyk.io/vuln/SNYK-JS-TREEKILL-536781

Author: snyk-bot

.snyk

@@ -1,5 +1,5 @@
 # Snyk (https://snyk.io) policy file, patches or ignores known vulnerabilities.
-version: v1.13.5
+version: v1.14.0
 ignore: {}
 # patches apply the minimum changes required to fix a vulnerability
 patch:
@@ -77,3 +77,8 @@ patch:
         patched: '2019-10-04T04:37:00.187Z'
     - marpat > snyk > proxy-agent > pac-proxy-agent > https-proxy-agent:
         patched: '2019-10-04T04:37:00.187Z'
+  SNYK-JS-TREEKILL-536781:
+    - snyk > snyk-sbt-plugin > tree-kill:
+        patched: '2019-12-12T07:52:09.956Z'
+    - marpat > snyk > snyk-sbt-plugin > tree-kill:
+        patched: '2019-12-12T07:52:09.956Z'