Add Postgraphile subscription exposure

- Add automation for TypeScript project build and tests via
  Webpack, tsc, and Jasmine
- Add custom Express application to serve Postgraphile
  subscription endpoints
- Add automated test suite for subscription endpoints

postgraphile/spec/support/jasmine.json

@@ -0,0 +1,11 @@
+{
+  "spec_dir": "build/spec/",
+  "spec_files": [
+    "**/*[sS]pec.js"
+  ],
+  "helpers": [
+    "helpers/*.js"
+  ],
+  "stopSpecOnExpectationFailure": false,
+  "random": true
+}