fix: .snyk to reduce vulnerabilities

The following vulnerabilities are fixed with a Snyk patch:
- https://snyk.io/vuln/SNYK-JS-LODASH-567746

Author: snyk-bot

.snyk

@@ -26,3 +26,9 @@ patch:
         patched: '2020-04-30T23:28:44.101Z'
     - '@babel/core > @babel/helper-module-transforms > @babel/helper-replace-supers > @babel/traverse > @babel/helper-function-name > @babel/template > @babel/types > lodash':
         patched: '2020-04-30T23:28:44.101Z'
+    - casbin > lodash:
+        patched: '2020-05-01T01:44:07.188Z'
+    - casbin-sequelize-adapter > casbin > lodash:
+        patched: '2020-05-01T01:44:07.188Z'
+    - casbin-sequelize-adapter > sequelize > lodash:
+        patched: '2020-05-01T01:44:07.188Z'