Fix 500 on trial mode page

I was using the trial mode page to prototype the time picker as part of
225a61ddd3.

I didn’t clean up properly, and left an errant undefined variable, which
caused the trial mode page to `500`.

This commit:
- removes the errant argument
- adds a test for all the static pages to make sure that they at least
  return a `200`

app/main/views/index.py

@@ -31,7 +31,7 @@ def cookies():
 
 @main.route('/trial-mode')
 def trial_mode():
-    return render_template('views/trial-mode.html', hours=hours)
+    return render_template('views/trial-mode.html')
 
 
 @main.route('/pricing')