Fix wrong hostname display

This is a fix to issue #13.

The hostname in the top of the html was wrongly displayed. That was due to hardcoded markup.

To fix the issue, I have added a new page handler, BaseHandler to handle all of the dynamic features that are out of the scope of specific handlers (such as the header, which is shared between all of the
handlers).

The base handlers listens to the route change event and updates shared dynamic information.