v0.9.0-alpha+7

• Material Button: Add compact mode.
• Material Expansionpanel: Add option show/hide the cancel button.
• Material Select:
  • Add option to dropdown to disable deselecting on trigger.
  • Allow content to be projected as list header and list footer in dropdown.
  • Implement Focusable in DropdownButtonComponent.
  • Fixed an alignment issue with the icon on dropdowns.
• Material Menu:
  • Trigger selected event when an item from sub-menu is selected.
  • Change mouse pointer on catagory to make it clear that it is clickable.
• Material Tooltip: Change tooltipSource directive to use style.cursor.
• Allow '[' for start of word of highlight match.
• Use @VisibleForTesting annotations.
• Prepare for change of async behavior in Dart 2.
• Make LazyEventEmitter no longer lazy and makes it easy to see why it should
  not be used and a StreamController can be a simple drop in replacement.
• Update documentation.