Add tests for plume webserver (#513)

* begin setup front-end test environment with selenium
* run migrations before tests
* use https for tests

.circleci/images/plume-buildenv/Caddyfile

@@ -0,0 +1,6 @@
+localhost:443 {
+  proxy / localhost:7878 {
+    transparent
+  }
+  tls self_signed
+}