Feature/12 introduce menu

[danielabar]

• a basic unstyled menu displaying a few options with radio buttons
• graph interaction model - shared state between graph menu and graph (to avoid overuse of pub-sub which can make app hard to follow)
• upgrade from Aurelia 0.16 to 0.17 to make use of bindingEngine for property observer
• some initial experimentation with sliding the menu down and up, via toggling show/hide css classes and css3 transitions

Fixes #12