Add flexible UI to support tablet devices

The graph and user interface now scale to the size of the client, to
accommodate tablet devices. Smartphones will be targeted in a future
releases, although they will require more work; due to their smaller
screens.

Improvements for future releases:

- The graph should adapt to the pixel density of the device, so that it
  does not appear blurry at very high resolutions.

- There should be an option to hide the control panel, so that the graph
  can fill the entire screen (especially important for mobile devices).

- Any resize or screen orientation events should be slightly delayed, in
  order to prevent them from 'locking up' the UI on smaller devices.
Add live demo links to README.md

Moving the 'Supported Browsers' section right below the links to the
new live demonstrations, should hopefully make it nice and obvious
to anyone still running IE6, etc.