* Check if `Backbone.history.start()` has been called before.
* Only call it after routes have been registered.
* Use route for switching between login and register forms

to validate required fields, instead of doing it manually.

All supported browsers have this feature.

instead of bundling all translations in the dist file.

This solves a bug whereby switching to the register form doesn't happen because
validation gets triggered which somehow prevents it.

This is a workaround for the fact that getttext doesn't support ES2015 template
literals and it also allows us to scan for translateable strings in our HTML
templates.

We can now simply call `render` whenever we want to show an error or
notification message.

The flip side is that the template is now larger and contains more login.

instead of manually

* Use declarative events instead of `addEventListener`.
* Remove the jquery dependency in this module

Somehow the tests are flaky when the router sets a URL fragment for login or
registration, so I've now added an event handler which does the work without
setting the URL fragment.

The router is still there so that one can manually link to a URL that has the
registration form open. (Issue #828)

* In certain places, use native methods instead of jQuery
* Nicer rendering of registration forms
* Use CSS3 fade-in animations.