shinywidgets 0.3.1

• Widgets no longer have a "flash" of incorrect size when first rendered. (#133)
• @render_widget now works properly with Widgets that aren't DOMWidgets (i.e., widgets that aren't meant to be displayed directly). As a result, you can now use @render_widget to gain a reference to the widget instance, and then use that reference to update the widget's value. (#133)