Air-gap: remove dead CDN reference + in-app /docs

- Removed a dead IE<9-only html5shim script tag pointing at a domain
  that no longer resolves.
- New GET /docs (index) and /docs/:slug routes render this project's
  own README, DEPLOYMENT, API.md, docs/*.md, and directory_spec.md
  server-side via marked -- so the documentation is readable from the
  running app with no route to GitHub Pages, where it otherwise only
  lives. Public, no auth, rate-limited (middleware/rate_limit.js) like
  the other public routes.
- .dockerignore/Dockerfile.openldap updated to copy DEPLOYMENT.md,
  API.md, directory_spec.md, and docs/ into the image, mirroring the
  existing tos.md -> /tos.md convention.

nodejs/app.js

@@ -68,6 +68,11 @@ app.use('/static', express.static(path.join(__dirname, 'public'), {maxAge: '1h'}
 // Routes for front end content.
 app.use('/', require('./routes/index'));
 
+// Local, in-app copy of the project's documentation (README, DEPLOYMENT,
+// API.md, docs/*) -- public, no auth, so it's readable even by a locked-out
+// admin or an air-gapped operator with no route to GitHub Pages.
+app.use('/docs', require('./routes/docs'));
+
 // API routes for authentication. 
 app.use('/api/auth',  require('./routes/auth'));