wip Slider widget
wip Slider widget
update slider css
add batch update support to the base Widget
use batching support with the push button
wip
Merge branch 'feature-slider' of https://github.com/nucleic/phosphor into feature-slider

Conflicts:
	src/styles/slider.css
	src/widgets/slider.js
update cursor util naming
add a token utility module
cleanup dom property and class name handling
update push button dom property handling
simplify the signaler
update the tree implementation
code formatting
code cleanup
isolate try-finally from rest of code for optimaization
add ability to silently update dom property
update method name
update the LineEdit to use deferred dom updates
update comments