Install testing packages for server, setup config

What:

1) Install jest and supertest
2) Set jest to ignore /dist, /static, /node_modules

Why:

1) supertest is useful for mocking http requests
2) Only test server/src

.env.example

@@ -1,4 +1,5 @@
 DATABASE_URL=postgres://<user>:<pw>@<instance>:5432/<db_name>
+TEST_DATABASE_URL=postgres://<user>:<pw>@<test_instance>:5432/<test_db_name>
 ALPHA_VANTAGE_KEY=
 JWT_SECRET=jonistheman
 SALT=10

client/package.json

@@ -8,7 +8,7 @@
     "serve": "vue-cli-service serve",
     "build": "vue-cli-service build",
     "test:unit": "vue-cli-service test:unit",
-    "test:e2e": "vue-cli-service test:e2e --mode development",
+    "test:e2e": "vue-cli-service test:e2e --mode test",
     "lint": "vue-cli-service lint",
     "jsdoc": "./node_modules/.bin/jsdoc . -c ./jsdocs.json -R ../README.md",
     "test": "npm run test:unit"