Started rewriting navbar buttons to use PushButton and ToggleNode, see #86
Show which navbar button is selected and fixed pickable flags for NavBar background and title, see #86
Fixed spacing and highlighting, see #86
removed unused variable
removed unused imports
reuse icon node
make sure navbar buttons are a certain minimum distance apart
updated docs
opt-out of wrapping children to improve performance, see #88
use setVisible instead of add/removeChild to switch screens (to improve performance), see #89
Darkened the 'h' further to make it visible against white, see #78
Rewrote the home button to use PushButton, see https://github.com/phetsims/joist/issues/90
Rewrote the PhetButton to use PushButton, see #91
removed unused code
Made highlight extend scenery.Node, see https://github.com/phetsims/joist/issues/92
removed unused code, see https://github.com/phetsims/joist/issues/92
Simplified use of highlight node, see https://github.com/phetsims/joist/issues/92
Made it possible to invert the highlights, see https://github.com/phetsims/joist/issues/78
Edited pickability
Moved HomeButton from scenery-phet to joist